The Tanzer 31 is a recreational keelboat built by Tanzer Industries of Dorion, Quebec from 1984 to 1986. It has a masthead sloop rig.
Designed by George Cuthbertson of Cuthbertson & Cassian, the fibreglass hull has a spade-style rudder and a fixed fin keel.
It is powered by an inboard Yanmar Diesel engine of , with a fuel tank. A fresh water tank was also fitted.
The boat has a PHRF racing average handicap of 168 with a high of 182 and a low of 159. It has a hull speed of .