The 1934 Mannin Moar (formally known as II Mannin Moar) was a Grand Prix that was held on 2 June 1934 at a street circuit in Douglas, Isle of Man, United Kingdom.

It was the twelfth round of the 1934 Grand Prix season, but it did not count towards the championship.

The race, contested over 50 laps of 3.659 mi, or 5.889 km, was won by Brian Lewis driving an Alfa Romeo Tipo B after starting from pole position.

Rose-Richards made the best start of the line, overtaking both Staniland and Dixon to get into second place after Lewis, who would eventually stay in the lead the entire race.

Although it was not an easy victory - his Alfa Romeo had lost a gear early in the race - Lewis took the flag after fifty laps ahead of Dodson and Paul.