The 1998–99 FIBA EuroLeague was the 42nd installment of the European top-tier level professional club competition for basketball clubs (now called simply EuroLeague).

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.

[1] For the 1998–1999 EuroLeague, the countries are allocated places according to their place on the FIBA country rankings, which takes into account their performance in European competitions from 1995–96 to 1997–98.

[2] The labels in the parentheses show how each team qualified for the place of its starting round:

(The individual scores and standings of the First round are accumulated in the Second round) If one or more clubs are level on won-lost record, tiebreakers are applied in the following order: