Panathinaikos Football Club (Greek: ΠΑΕ Παναθηναϊκός Α.Ο. , known as Panathinaikos, or by its full name, and the name of its parent sports club, Panathinaikos A.O. or PAO (Παναθηναϊκός Αθλητικός Όμιλος; Panathinaïkós Athlitikós Ómilos, "All-Athenian Athletic Club"), is a Greek professional football club based in the capital-city of Athens.

The name "Panathinaikos" was inspired by the ancient work of Isocrates, Panathenaicus, where the orator praises the Athenians for their democratic education and their military superiority, used for the benefit of all Greeks.

Today a part of Panathinaikos A.O., they are the oldest active football club in Greece, initially founded only to practice this sport. Created in 1908 as "Podosfairikos Omilos Athinon" (Football Club of Athens) by Georgios Kalafatis, they play in the Super League Greece, being one of the most successful clubs in Greek football and one of three clubs which have never been relegated from the top division. Amongst their major titles are 20 Greek Championships, 18 GreekCups, achieving eight times the Double, and 3 Greek Super Cups. They are also one of the two clubs that won a championship undefeated, going without a loss in a top-flight campaign in the 1963–64 season.

Panathinaikos is also the most successful Greek club in terms of achievements in the European competitions. It is the only Greek team that has reached the European Cup (later renamed UEFA Champions League) final in 1971 (which they lost to Ajax Amsterdam 2–0), and also the semi-finals twice, in 1985 and 1996. It is also the only Greek team that has played for the Intercontinental Cup (1971). Furthermore, they have reached the quarter-finals of the Champions League on another two occasions (in 1992 and 2002), as well as the quarter-finals of the UEFA Cup twice (1988 and 2003). They have also won the Balkans Cup in 1977. Panathinaikos is a member of the European Club Association.