The 2005 Monaco Grand Prix Formula Three was a Formula 3 Euro Series motor race held on 20 and 21 May 2005 at the Circuit de Monaco in Monte Carlo, Monaco.

It was the fourth race of the 2005 Formula 3 Euro Series.

It was the first time Formula Three cars had raced at Monaco since 1997, and remains the last to date.

The race was used to support the 2005 Monaco Grand Prix.