The 2005–06 Croatian First Football League (officially known as the Prva HNL Ožujsko for sponsorship reasons) was the fifteenth season of the Croatian First Football League, the national championship for men's association football teams in Croatia, since its establishment in 1992.
Hajduk Split were the defending champions, having won their eighteenth championship title the previous season.
Dinamo Zagreb won the title, after a win against Osijek on 6 May 2006, which started his eleventh year dominance.
Playoff wasn't needed after the second-placed Croatian Second Football League team, Belišće, failed to secure a license to compete in Prva HNL.
Therefore, Međimurje automatically kept their first-league status for the 2006–07 season.