Professional Foul is a television play written by Czech-born, British playwright Tom Stoppard. It was broadcast on 21 September 1977 in BBC 2's Play of the Week series.

The play is set in Prague and follows the character of Professor Anderson, a Cambridge ethics don, on a weekend visit to a philosophical colloquium. What should be a fairly uneventful trip is complicated by the intervention of the Communist government, leading to an ethical dilemma for the professor of philosophy, a situation explored by Stoppard through the opinions of several characters.

The play was written to coincide with Amnesty International's "Prisoners of Conscience Year" and is dedicated to Czech playwright Václav Havel, then periodically imprisoned by the Czech Communist authorities. Stoppard has cited Havel as an influence on his writing. In the year of publication and broadcast the Charter 77 movement in Czechoslovakia presented the government with a formal protest against its violations of the Helsinki Accords. Havel would later go on to be the President of Czechoslovakia and the Czech Republic.

Owing to its television broadcast and Stoppard's desire to convey his anti-totalitarian message to the largest audience possible, Professional Foul is less structurally and linguistically complex than some of his other works, though various examples of word play and philosophical language appear in the play. Stoppard would return to the theme of resistance against the Communist Party of Czechoslovakia in the plays Dogg's Hamlet, Cahoot's Macbeth and Rock 'n' Roll.

Through the piece's 16 scenes the action almost exclusively revolves around Anderson with only one brief scene not involving the character, a marked change of emphasis from Stoppard's earlier works.

The play was published by Faber & Faber with another of Stoppard's plays, Every Good Boy Deserves Favour in 1977.

Stoppard adapted Professional Foul for BBC Radio 4 which was broadcast on 11 June 1979, starring Peter Barkworth and John Shrapnel and other of the original BBC TV play.