It lies 40 kilometres (25 mi) northwest of Oslo and is the nation's fifth largest lake with an area of 138.56 km2.

Its primary outlet is at Vikersund near the lake's southwest corner, where Tyrifjorden discharges into the Drammenselva river.

Tyrifjorden is located in the county of Buskerud and borders the municipalities of Hole, Lier, Modum, and Ringerike.

It consists of a main body, Storfjorden, along with the Holsfjorden, Nordfjorden, and Steinsfjorden branches.

On 22 July 2011, an island in the lake, Utøya, was the site of a shooting spree during a youth camp held by the Norwegian Labour Party.