West Ham first travelled into Europe to play football in 1921 when manager Syd King took the team to Spain where they played games against Real Madrid, Celta de Vigo, Athletic Bilbao and Deportivo de La Coruña. In the early 1960s, West Ham travelled abroad to play frequently with matches in Costa Rica, Sweden, Rhodesia, Ghana, the United States, Austria and West Germany.
After winning the previous season's FA Cup, manager Ron Greenwood led West Ham into their first European campaign. Two goals from Alan Sealey saw West Ham win the competition against West German side 1860 Munich before a crowd of 100,000 at Wembley on 19 May 1965.
West Ham started the competition against La Gantoise, the first Belgian side to play in this competition. In the opening game on 23 September 1964, West Ham won 1–0 in Belgium thanks to a headed Ronnie Boyce goal from an Alan Sealey corner. In the home leg, West Ham fans paid record match receipts to see what was described as a "decrepit performance which brought jeers from the crowd". Martin Peters scored an own goal for La Gentoise before Johnny Byrne scored an equalizer from a cross by Johnny Sissons In the second round, West Ham drew Czech side Sparta Prague.
The first leg on 25 November contained considerable time-wasting by the Czechs including four times when the ball was kicked clean out of the ground. The match was decided in the second half by a 25-yard shot from full-back, John Bond, his first for three years and Alan Sealey, who scored after his shot had hit the post. In the second leg, on 9 December 1964, Sissons put West Ham 3–0 up on aggregate only for Prague's Gustáv Mráz to score two late goals to finish the tie 3–2 in favour of West Ham. The quarter-finals matched West Ham against Swiss side Lausanne. In the first leg in Switzerland, Brian Dear, playing in his first European game scored the first goal, Byrne the second before Lausanne scored in the 80th minute through Robert Hosp. The second leg, described as a "thrilling cup-tie" took place at the Boleyn Ground on 23 March 1965. Two goals from Dear, one from Peters and an own goal from Lausanne's Ely Tacchella gave West Ham an aggregate 6–4 win. The Lausanne goals were scored by Pierre Kerkhoffs, Hertig and Norbert Eschmann. The semi-finals West Ham played Spanish side, Real Zaragoza. In the first leg in London, West Ham scored two first-half goals through Dear and Byrne. They attempted to defend their lead in the second half by playing nine in defence but conceded a 55th goal scored by Canário. The second leg in Spain finished as a 1–1 draw with goals from Sissons and Zaragoza's Carlos Lapetra. Zaragoza were denied three penalty appeals and blamed the referee for their defeat. The final against West German side 1860 Munich was played at Wembley on 19 May 1965 in front of 100,000 spectators. It has been described as "West Ham's greatest moment". Alan Sealey scored in the 69th and 71st minute, the first from an "impossible angle" and the second after Bobby Moore's free-kick was not cleared by the Munich defence. Manager Greenwood, in his 1984 book Yours Sincerely, noted the significant roles played by Sealey, Dear and Bobby Moore in the final but also praised West Ham's defence, particularly the efforts of goalkeeper Jim Standen and defender Jack Burkett.
After winning the previous season's Cup Winners' Cup West Ham began another campaign in the same competition losing in the semi-final to eventual winners, Borussia Dortmund.
As the holders, they received a bye in the first round. In the second round, they played Greek side Olympiacos. In the first leg at the Boleyn Ground, West Ham won 4–0 with goals from Johnny Byrne, Peter Brabrook and two from Geoff Hurst. The away leg a week later finished 2–2. In a game refereed by future 1966 FIFA World Cup Final linesman Tofiq Bahramov, Martin Peters scored twice for West Ham with an own goal by Eddie Bovington and an 80th penalty by Kostas Polychroniou for Olympiakos. East German team, 1. FC Magdeburg were West Ham's opponents in the quarter-finals. The East Germans spent much of the game defending in the first leg in London and were beaten only by a single goal, by Johnny Byrne. In Magdeburg, Joachim Walter scored in the 78th minute to make the game 1–1 on aggregate. Johnny Sissons equalized almost from kick-off, in the 79th minute, to put West Ham through 2–1. West Germany provided the opponents in the semi-finals with Borussia Dortmund. Bobby Moore, who had stated his desire to leave the club, was replaced as captain by Johnny Byrne. The West Germans won 2–1 at the Boleyn Ground. Although Martin Peters scored first, Lothar Emmerich scored in the 86th and 87th minute to take a lead to the second leg in Dortmund. On 13 April in West Germany, Dortmund scored in the first minute through Emmerich, who added another in the 28th minute and although Peters scored to make the game 2–4 on aggregate, Gerhard Cyliax scored a third Dortmund goal in the 87th minute to put them through to the final, 5–2 on aggregate.
Winners of the 1975 FA Cup, West Ham – now managed by John Lyall – again entered the Cup Winners' Cup, eventually losing in the final to Anderlecht.
West Ham started this campaign with an away game against Finnish side, Lahden Reipas. The match was played in the Helsinki Olympic Stadium in front of a crowd of just 4,587. Lahden Reipas took the lead in the fourth minute through Harri Lindholm after his shot had hit West Ham goalkeeper Mervyn Day in the chest and gone in. Trevor Brooking equalized in the 58th minute with a free-kick only for the home side to take the lead in the 55th minute through Ari Tupasela. Billy Bonds scored in the 76th minute to leave the match level going into the second leg. In the return leg in London, West Ham ran out 3–0 winners thanks to goals from Keith Robson, Pat Holland and Billy Jennings.
West Ham's next opponents were Ararat Erevan in Armenia in the Soviet Union. Alan Taylor scored to take the lead only for Erevan's Samvel Petrosyan to head the ball out of Mervyn Day's hands. With the West Ham players expecting the goal to be disallowed, West German referee Hans-Joachim Weyland allowed it, making the game 1–1. In the home leg in London on 5 November, West Ham won 3–1 with goals from Robson, Taylor and Graham Paddon. Erevan's single goal was scored by Nazar Petrosyan.
In the quarter-finals, West Ham faced Dutch side FC Den Haag. In the first leg in the Netherlands, 1970 World Cup Final referee Rudi Glöckner awarded Den Haag two penalties for handball. Both were scored by Aad Mansveld, who added a third for his hat-trick. Lex Schoenmaker scored their fourth goal with West Ham's two goals coming from Billy Jennings. In the second leg on 13 March 1976, West Ham scored three first-half goals through Alan Taylor, Frank Lampard and Billy Bonds to make the game 5–4 to West Ham. Lex Schoenmaker scored in the 59th minute to tie the game 5–5. West Ham survived a tense last half-hour of the game and went through on the away goals rule.
West German's Eintracht Frankfurt stood between West Ham and a cup final appearance. In the first-leg in West Germany, Frankfurt played their reserve goalkeeper, Peter Kunter, a part-time player who is also a dentist. He was beaten after only nine minutes by Graham Paddon's 30 yards (27 m) shot. Frankfurt scored two goals through Willi Neuberger and Wolfgang Kraus to take a 2–1 lead to London. West Ham won 3–1 in the home leg. Two from Trevor Brooking and one from Keith Robson were enough to give the tie 4–3 to West Ham with a goal for Frankfurt's Klaus Beverungen. Goalkeeper Mervyn Day won particular praise from the manager for his saves in the first half.
The final was played at the Heysel Stadium in Brussels against Anderlecht. Pat Holland opened the scoring in the 29th minute but Frank Lampard's poor back-pass allowed Rob Rensenbrink to equalise. François Van der Elst added another in the 48th minute and although Keith Robson equalized with a header, both man-of-the-match Rensenbrink and Van der Elst scored again to give Anderlecht the trophy.
Winners of the 1980 FA Cup, West Ham a Second Division team, started another European campaign in the Cup Winners' Cup. Crowd violence broke out in the first-leg away in the Bernabéu Stadium to Castilla in which one West Ham fan was killed. West Ham were ordered to play the return leg at least 300 kilometres (190 mi) from Upton Park. After an appeal, they were allowed to play at home resulting in the playing of "the Ghost Match" behind closed doors in the return leg at Upton Park with no fans in attendance, resulting in an official attendance of 262, the club's lowest ever figure for a competitive first team match. 3–1 down from the first-leg, West Ham won the second-leg 5–1, still their record score in European football with David Cross scoring a hat-trick, West Ham's only ever hat-trick in European competition. In the second round, West Ham played Romanian side Poli Timișoara. The first-leg in London resulted in a 4–0 win for West Ham. Goals for Billy Bonds, Paul Goddard, a Ray Stewart penalty and another for David Cross gave them a strong lead ahead of the away leg. In Romania, Timisoara won 1–0 after Phil Parkes had let a Dan Păltinișanu shot bounce over his arm. West Ham lost in the quarter-finals to eventual winners Dynamo Tbilisi. In the first leg in London, West Ham lost 4–1. Tbilisi's performance was described as "one of the finest many fans had seen". They were 2–0 ahead by half-time after goals by Aleksandre Chivadze, Vladimir Gutsaev and although David Cross scored for West Ham, Ramaz Shengelia scored twice for the Soviets. In the away leg in Tbilisi, West Ham needed to score four goals which never looked likely. They won 1–0, in the Lenin Stadium, after an 88th-minute goal by Stuart Pearson, losing the tie 2–4 on aggregate.
Following their fifth-place finish in the previous season's Premier League, West Ham, now managed by Harry Redknapp, entered the Intertoto Cup. Given a bye for the first two rounds, West Ham drew Finnish side Jokerit in the third round. In a poorly-attended first leg at the Boleyn Ground on 17 July 1999, West Ham won 1–0 with a goal from Paul Kitson. Manager Harry Redknapp blamed a disappointing performance on "midsummer lethargy". In Finland, Jokerit took the lead through Koskela before Frank Lampard Jr. equalized in the 70th minute with a 20-yard free-kick to put West Ham into the next round. Lampard scored again in the first leg of the next round, against Dutch side Heerenveen. His 25 yards (23 m) shot was enough to give West Ham the lead going into the second leg. 1–0 was also the score in the away leg on 5 August 1999. Following a 30 yards (27 m) Lampard shot which the goalkeeper failed to hold, Paulo Wanchope followed up to score and take West Ham into the final. Following a two-leg final against Metz in which they were 1–0 down from the home leg following a Metz goal from Louis Saha, West Ham won the away leg 1–3 at Saint-Symphorien Stadium with goals by Trevor Sinclair, Frank Lampard and Paulo Wanchope. West Ham therefore qualified for the UEFA Cup as one of the three winners of the competition for that season.
As winners of the 1999 Intertoto Cup, West Ham gained entry to the 1999–2000 UEFA Cup, the first time the club had qualified for the UEFA Cup in their history. In the first round, they beat Croatian side Osikek. They won the home leg 3–0 with goals from Paulo Wanchope, Paulo Di Canio and Frank Lampard Jr.. The away leg was a 1–3 West Ham victory, with goals coming from Paul Kitson, Neil Ruddock and Marc-Vivien Foé. Osijek's single goal was scored by Stanko Bubalo. In the second round, West Ham faced Romanian team Steaua București, going down 2–0 in the first-leg, following goals from Laurentiu Rosu and Sabin Ilie. The return leg at Upton Park ended 0-0 with West Ham being eliminated.
As runners-up in the 2006 FA Cup West Ham, now managed by Alan Pardew, gained entry to the 2006–07 UEFA Cup. Violence involving West Ham supporters was again in evidence. Twenty West Ham fans appeared in an Italian court following their arrest after fights with rival supporters in Sicily before and after West Ham's game against Palermo in the away leg of their 2006–07 UEFA Cup game. At the home leg, fans had bought T-shirts bearing the slogan "The Mafia" – a reference to Sicily being the home of the Cosa Nostra. This was seen as antagonistic by Palermo fans. Six West Ham fans, six police officers and five locals suffered minor injuries in fighting in Sicily. Rival fans threw bottles and chairs in the city's Teatro Massimo district. Five-hundred people were involved in the brawl and police officers were attacked. It took police in riot gear more than an hour to bring the violence under control. An eyewitness said, "West Ham fans behaved like animals, roaming the streets, bottles in hand searching for anyone to fight." More than 2,500 West Ham fans travelled to Palermo for the game.
West Ham lost the tie 4–0 on aggregate losing 0–1 at home to an Andrea Caracciolo goal and 3–0 in Palermo following two goals by Fábio Simplício and one by David Di Michele. Manager Alan Pardew gave full debuts to recent signings and Argentine internationals Javier Mascherano and Carlos Tevez in the games. Pardew had claimed before the games against Palermo that West Ham were in the competition to win it. They exited in the first round.
By winning the Premier League Fair Play table for 2014–15, West Ham qualified for the 2015–16 UEFA Europa League entering at the first qualifying round. In the first qualifying round, they were drawn against Andorran team Lusitanos, who qualified for the Europa League after finishing second in the 2014–15 Primera Divisió. Originally scheduled to play the away leg first, as two teams from Andorra were both scheduled to play at home on the same day, the legs were reversed with the home leg at the Boleyn Ground due on 2 July 2015. The second leg, on 9 July, was moved to the 1,300 capacity Estadi Comunal d'Andorra la Vella with West Ham supporters receiving a ticket allocation of 450. West Ham won the first leg 3–0 with two goals from Diafra Sakho and one from captain on the night James Tomkins. In front of a sell-out crowd, development side player and 16-year-old Reece Oxford made his debut to become West Ham's youngest player. There were also debuts for Lewis Page, Josh Cullen and Djair Parfitt-Williams. In the return leg in Andorra on 9 July, West Ham won 0–1. Elliot Lee, on his first start for the club, also scored his first West Ham goal. Sakho was sent-off in the 14th minute for violent conduct and there was a first full start for Josh Cullen and a first team debut for Amos Nasha.
In the second qualifying round, West Ham were drawn against Maltese side Birkirkara, who had beaten Armenian side Ulisses in the first round. Having played with several youth team players in the first leg, manager Slaven Bilić brought in more first-team players for the second round, including captain Kevin Nolan, Mark Noble, Winston Reid and Aaron Cresswell. Although they dominated possession, West Ham had to wait until a 90th-minute goal by James Tomkins gave them the victory. There was a debut in the game for recent signing from Manchester City, Martin Samuelsen. West Ham struggled in the away leg, losing 0–1 to a goal by Fabrizio Miccoli in the 14th minute. James Tomkins for West Ham and Mauricio Mazzetti for Birkirkara were sent-off. West Ham had only one shot on target as the game went to extra-time having finished 1–1 on aggregate after 90 minutes. They won the tie 5–3 on penalties, with Diego Poyet scoring the decisive penalty.
In the third qualifying round, West Ham drew Romanian side Astra Giurgiu, who had beaten Scottish team Inverness Caledonian Thistle in the previous round. In the first leg on 30 July, West Ham took a 2–0 lead with goals from Enner Valencia and Mauro Zárate before James Collins was sent-off. Fernando Boldrin scored before West Ham's Angelo Ogbonna, on his debut, scored an own goal to make the score 2–2. Manager Slaven Bilić was also sent to the stands after complaining about refereeing decisions. In the second-leg, on 6 August, Julian Dicks took charge of the team with Bilić sitting in the stands. Days away from the start of the Premier League season, 11 changes were made to the side which played in London. There were debuts for Kyle Knoyle, Manuel Lanzini, Doneil Henry, Jordan Brown and Alex Pike. Although Lanzini scored after three minutes, captain Constantin Budescu scored two goals for Astra Giurgiu in four minutes to put the Romanian side 1–2 ahead. With no further scoring, West Ham were eliminated 4–3 on aggregate.
West Ham United qualified for the 2016–17 UEFA Europa League on 21 May 2016, following Manchester United's 2–1 victory in the FA Cup final against Crystal Palace. With Manchester United having already secured a place in the competitions's group stage with a fifth-placed finish in the 2015–16 Premier League, their cup winners' slot passed to West Ham in seventh.
The draw for the Third qualifying round was made on 15 July 2016, with West Ham being drawn against Domžale of Slovenia, after they defeated Shakhtyor Soligorsk from Belarus in the second qualifying round. West Ham were originally drawn to play the first leg at their new home, the London Stadium, but due to a clash with the Anniversary Games, the club received permission from UEFA to reverse the order of the legs. The away leg was switched from Domžale's Sports Park ground, to the 16,038 capacity Stožice Stadium in Ljubljana, home of the Slovenia national team. West Ham lost the first leg away in Slovenia on 28 July, with Matic Črnic scoring a penalty in the 11th-minute after a handball by debutant Håvard Nordtveit, only for Mark Noble to equalize from the penalty-spot seven minutes later, after Winston Reid was fouled by Domžale's goalkeeper Axel Maraval. Črnic scored a second goal three minutes into the second half to give the Slovenians a 2–1 victory. Seven days later, West Ham hosted Domžale in the club's first ever game in their new home, the London Stadium. West Ham won 3–0 with two goals from Cheikhou Kouyaté and a third from Sofiane Feghouli, resulting in a 4–2 aggregate victory to progress to the play-off round.
On 5 August, West Ham were drawn to play Romanian Liga I champions Astra Giurgiu in the play-off round. Astra eliminated West Ham from the same competition 12 months earlier in the third qualifying round 3–4 on aggregate, and became the first side West Ham have drawn twice in European football. The first leg took place on 18 August at Stadionul Marin Anastasovici in Giurgiu, with the game finishing in a 1–1 draw. Mark Noble had given West Ham the lead just before half-time with a penalty, after a handball by Cristian Săpunaru. Astra equalised seven minutes from time, when Denis Alibec turned James Collins to score. There were debuts for new signing Jonathan Calleri and academy graduate Marcus Browne. On 25 August, West Ham lost the home leg 0–1, with Astra's Filipe Teixeira scoring the only goal of the game in the 44th minute. West Ham exited the competition for the second year running to the Romanian side.Correct as of 18 August 2016, vs. Astra Giurgiu
Bold indicates player still at West Ham United
Bold/Italics indicates player currently out on loan
The following is a list of West Ham United's goalscorers in official UEFA competitions (not to include Anglo-Italian Cup statistics):
As well as being involved in a Cup Winners' Cup campaign, West Ham participated in the Anglo-Italian League Cup, a short-lived competition played between the winners of the FA Cup and the Coppa Italia. The first leg took place in Florence at the Stadio Artemio Franchi on 3 September 1975, with Fiorentina's Vincenzo Guerini scoring the only goal of the game. In the second leg at Upton Park, Fiorentina again won 1–0, this time with the goal coming from Walter Speggiorin to seal a 2–0 aggregate victory for the Italians.
The revival of the Anglo-Italian Cup for the 1992–93 campaign saw West Ham, under the management of Billy Bonds, return to European competition for the first time since 1980–81. West Ham started the campaign in a domestic qualifying stage to decide which English clubs would play Italian sides. Their first game on 2 September 1992 was a 2–2 home draw against Bristol Rovers, with both West Ham goals scored by Julian Dicks. The second game was on 30 September against Southend United at Roots Hall. West Ham won the game 3–0 with goals from Dicks, Trevor Morley and Matty Holmes. As a result, They won their preliminary group and qualified for the full competition. This failed to attract interest from fans, however, with attendances as low as 800 away to Cosenza and 1,639 at Cremonese. Of the four games played against Italian opposition West Ham won two, drew and lost one game each. They lost 0–2 away to Cremonese in their opening group game, before beating Reggiana 2–0 at Upton Park, with both goals coming from Clive Allen. Against Cosenza, they won 1–0 away in Italy, with the single goal coming again from Allen. In their final match, West Ham drew 0–0 with Pisa at Upton Park. West Ham were eliminated after finishing third in the English section of the group, with only the best-placed English (Derby County) and best-placed Italian teams (Cremonese) progressing to the next round.