The 1998/99 season of the Portuguese First Division began on August 21 and ended on May 30.
FC Porto became champions for the fifth time in a row.
These teams were promoted from the Portuguese Second Division of Honour at the start of the season: These teams were relegated to the Portuguese Second Division of Honour at the end of the season: The final of the Cup was surprisingly between two minnows, SC Beira-Mar – who had just been relegated – beating SC Campomaiorense 1–0,[1][2] after the precocious elimination of all stronger clubs, with FC Porto and S.L.
Benfica being eliminated in the round of 32 and Sporting CP in the round of 64.