On 10 March 1925, Olympiacos formed from the merger of two other clubs and have since become Greece's most successful team with a record 44 league titles.
The two previous clubs, both based in Piraeus, dissolved in order to create a unified club for the area, which took the name Olympiacos Syndesmos Filathlon Piraios ("Olympiacos Club of Fans of Piraeus") and chose red and white as their colors.
The first Greek national league began competition with the 1927-28 season and Olympiacos quickly became the country's dominant club, winning their first title in 1931 and taking five more in the next seven seasons. They have won multiple titles in each decade, including an impressive run starting in 1997 that has seen them win all but two of the league titles since then (they finished as runners-up in 2004 and 2010). They have also won a record 27 Greek Cups.
They have a strong rivalry with Panathinaikos, known as the Derby of the Eternal Enemies. Olympiacos have had the better of it, winning 80 games to 50 for Panathinaikos, with 67 draws.