The 1998–99 Slovak First Football League (known as the Mars superliga for sponsorship reasons) was the sixth season of first-tier football league in Slovakia, since its establishment in 1993.

FC Košice were the defending champions.

A total of 16 teams was contested in the league, including 14 sides from the 1997–98 season and two promoted from the 2.

Lokomotíva Košice and FK DAC 1904 Dunajská Streda was relegated to the 1998–99 2.

The two relegated teams were replaced by FC Nitra and ZTS Kerametal Dubnica.