The 1998–99 FIBA EuroLeague was the 42nd installment of the European top-tier level professional club competition for basketball clubs. It began on September 23, 1998, and ended on April 22, 1999. The competition's Final Four was held at Olympiahalle, Munich, with Žalgiris defeating Kinder Bologna in the EuroLeague Final, in front of 9,000 spectators.

The EuroLeague, known as the Turkish Airlines EuroLeague for sponsorship reasons, is a European men's professional basketball club competition. The league is widely recognised as the top-tier men's league in Europe. The league consists of 18 teams, of which 16 are given long-term licences and wild cards, making the league a semi-closed league. The league was first organized by FIBA in 1958, subsequently by ULEB in 2000 and then solely the Euroleague Basketball.