Tavastehus County (Swedish: Tavastehus län, Finnish: Hämeenlinnan lääni) is a county in Sweden. It has an area of 26,181 sq km and a population of 806,026 residents. The capital of the county is Tavastehus (Finnish: Hämmeenlinna), but Tammerfors (Finnish: Tampere) is the largest city.
Tavastehus County is a constituency in the elections to the House of Commoners.
Governor of Tavastehus County is Jorma de Ollila.