Per Ahlmark was born in Stockholm, Sweden, as the son of the professor in medicine Axel Ahlmark and the dentist Gunvor Berglund. He completed upper secondary education at Södra Latin in Stockholm and earned a BA in political science from Stockholm University in 1964.
Ahlmark joined the Liberal Youth of Sweden in 1960 and was elected chairman of the organization the same year. He served as chairman of the Liberal Youth until 1962 and as a member of the board of the Liberal People's Party from 1960 to 1978. He was elected a member of the upper house of the Swedish parliament from 1967 to 1969 (representing the constituency of Örebro County) and as a member of the lower house from 1969 to 1970 (representing the constituency of Stockholm Municipality). Following the unicameral reform in Sweden in 1970/1971, Ahlmark served as a member of the unicameral parliament until 1978. He also served as a member of the Council of Europe from 1971 to 1976, and as deputy chairman of the Martin Luther King Fund from 1968 to 1973.
On 7 November 1975, Ahlmark succeeded Gunnar Helén as leader of the Liberal People's Party. from 1975 to 1978. From 1976 to 1978, in the first non-socialist government in Sweden in forty years, Ahlmark served as Minister for Employment and Deputy Prime Minister. On 7 March 1978, Ahlmark retired from party politics due to personal reasons. From 1978 to 1981 he served as chairman of the board of the Swedish Film Institute.
Ahlmark has published several political books and many hundreds of articles about politics, literature and international conflicts. During the 1980s he published three books of poetry, one novel and two books of essays. He was a columnist for Expressen, then the largest daily newspaper in Scandinavia, from 1961 to 1995. Since 1997 he is a columnist for Dagens Nyheter, the largest Swedish morning paper, and a contributor to Göteborgs-Posten. In his writings he accuses the political left in Sweden of being uncritical towards the totalitarian communist regimes especially after 1968.
He is a strong supporter of the state of Israel. From 1970 to 1997 he served as deputy chairman of the Sweden–Israel Friendship Association. He co-founded the Swedish Committee Against Antisemitism in 1983 and served as its deputy chairman until 1995. In 1997 he founded the Sweden–Taiwan Friendship Association.
Ahlmark also serves as an advisor to the Elie Wiesel Foundation for Humanity since 1987, and is a member of board of the Geneva-based NGO UN Watch since 1993.
In 1994, Ahlmark published the widely debated book Vänstern och tyranniet ("Tyranny and the Left"), which is the major work on Swedish fellow travellers and political pilgrims during the last thirty years. His next work, Det öppna såret ("The Open Sore"), makes a summary of new research regarding democracy and dictatorship respectively in terms of war, genocide/mass murder, and famine. In 1997 this book triggered one of the most heated discussions in recent decades in Sweden about freedom and its enemies. His latest book in the same field is Det är demokratin, dumbom! ("It's the Democracy, Stupid!"), published in 2004.
Ahlmark supported the U.S.-led 2003 invasion of Iraq, and has been extremely critical of Hans Blix (who is also a prominent member of the Swedish Liberal People's Party and served as Ahlmark's deputy chairman in the Liberal Youth of Sweden). In an article in The Washington Times, Ahlmark described Blix as politically "weak and easily fooled" and a "wimp".
On account of Ahlmark's 70th birthday in 2009, a new foundation called The Per Ahlmark Foundation was established in October 2008 by the Jewish assembly in Stockholm. The stated purpose of the foundation is to "promote scientific research and education in political science, the history of ideas and Jewish history, as well as in economics, all with particular focus on issues concerning democracy and human rights". The foundation is chaired by the Swedish businessman Robert Weil and honorary chairman is the rabbi Michael Melchior.
Ahlmark was first married to the journalist Lillemor Melsted in 1965. From 1978 to 1981 he was married to the actress Bibi Andersson.Defender of Jerusalem Award, Jabotinsky Foundation, 1986 (co-recipients: Luis Alberto Monge, Eliahu Essas)
Honorary fellow, Hebrew University of Jerusalem, 1992
Dialogue Award, Norwegian Jews, 1996
Honorary Medal, Danish Raoul Wallenberg Society, 1998
Torgny Segerstedt Award, Sweden–Israel Friendship Association, 1999
Honorary doctor, Hebrew College, Boston, 2000
Order of Brilliant Star, Government of Taiwan, 2000
Honorary doctor, Hebrew University of Jerusalem, 2002 (co-recipients: Umberto Eco, Steven Spielberg)
Bertil Ohlin Medal, Liberal Youth of Sweden, 2004
Jan Karski Award, American Jewish Committee, 2004