Ypäjä is a rural municipality located in the Kanta-Häme region of south-western Finland. It covers a total area of 183.25 square kilometres, with approximately 0.5 square kilometres consisting of water. The population density of the area is 11.96 inhabitants per square kilometre.
As of December 31, 2025, the municipality has a population of 2,186 residents. Ypäjä is unilingually Finnish.