Rudolph was elected king of West Francia in 923 by an assembly of Frankish nobles, to succeed his father-in-law Robert I who was killed in battle against the deposed king Charles the Simple. He was crowned by Walter, Archbishop of Sens at St.Médard in Soissons on Sunday, 13 July 923. On assuming the crown he passed the Duchy of Burgundy to his younger brother Hugh the Black.
In contemporary Latin documents, his name is usually Rodulfus, from the Germanic roots hruod, "glory", and wulf, "wolf". Rodulf and Rudolf are variants of this name; the French form is Rodolphe. By contrast, the king is normally known as Raoul in modern French, a name which derives from Radulfus, from Germanic rad, "counsel", and wulf. Although this name is of different origin, it was sometimes used interchangeably by contemporaries with Rodulfus. The king himself, however, always used Rodulfus, as on his personal seal. Nonetheless, he is sometimes called Ralph (from Raoul) or Radulf in English.
The deposed Charles the Simple was still alive and claimed the throne. This was solved when Rudolph's brother-in-law, Herbert II, Count of Vermandois, who was married to Emma's sister, tricked Charles, a fellow Carolingian, into meeting and then took him prisoner.
Rudolph's first act was to lead an army against the king of East Francia Henry the Fowler, who had made a pact with King Robert I at Jülich earlier in the year. After trying to annex Lotharingia Henry met Rudolph with a considerably-sized army and made peace again. However, in 925 Henry attacked Gilbert, Duke of Lorraine and took over Lotharingia permanently, Rudolph being in no position to resist.
In 924 Vikings made a fresh series of raids into West Francia. From the Loire Valley they threatened Hugh the Great, brother of Queen Emma, but Rudolph did nothing. Soon they attacked Burgundy, the domain of Rudolph's brother. They were repulsed, and moved on to Melun, where they threatened the royal lands. Joined only by his ecclesiastic vassals and Herbert, he recruited troops in Burgundy, while Hugh the Great was convinced to join him. After the Vikings left, the Normans, whom Charles the Simple had settled in Duchy of Normandy in 911, began ravaging that whole region. Herbert and Arnulf I of Flanders joined Rudolph and together they took Eu, but were ambushed near Fauquembergues where the king was wounded, the Count of Ponthieu killed, and many Normans left dead on the field.
Also in that year, Rudolph conversed with Louis the Blind, king of Provence, over the Magyars, the newest barbarian migrants to Europe, then menacing Louis. In 930 Magyars invaded the region around Rheims, but left before the king could engage them. In 935 Magyars invaded Burgundy and Rudolph brought a large army against them, causing their retreat without a battle. West Francia was temporarily safe from both Vikings and Magyars at Rudolphs's death.
In order to increase his own power, Herbert II, Count of Vermandois used his royal prisoner as a bargaining tool to secure the archbishopric of Rheims for his son Hugh in 925 and the county of Laon for his son Odo in 927. The complaints from Rudolph led Herbert II to bring Charles before William Longsword, Count of Rouen (sometimes incorrectly dubbed "Duke of Normandy"), for homage and then to Rheims to press Charles' claim on Pope John X. In 928 Herbert II finally got possession of Laon, but the next year Charles died at Péronne and Herbert II lost his leverage against Rudolph.
After defeating Vikings of the Limousin, Rudolph received the allegiance of the Aquitainians and homage from William Longsword, to whom he granted in 933 the islands off the coast of Normandy, now referred to as the Channel Islands.
In 929 Rudolph attempted to reduce the power of Ebalus, Duke of Aquitaine. He withdrew from him access to Berry, and in 932 granted the title of prince of Gothia to the count of Toulouse, Raymond Pons, and his brother of Rouergue, Ermengol. He also transferred the title Count of Auvergne to Raymond. Moreover, the territory of the march which was under the control of the lord of Charroux was transformed into an independent county. Later, however, Rudolph was campaigning with Ebalus in the south to eradicate the last Viking strongholds there. He then proceeded aggressively against Herbert II, marching into Rheims and replacing Hugh with Artald in 931. Then, joined by Hugh the Great, Rudolph burned Herbert's fortresses and cornered him in Château-Thierry, where he had first imprisoned Charles, from 933 to 934. The two made peace in 935 and Rudolph fell ill, dying a few months later on 14 or 15 January 936.