Trosa is a town in Södermanland County, with 5 000 citizens in the town itself, and 12,000 in total in Trosa municipality, Trosa kommun.
The other dominant settlement is Vagnhärad, at the Stockholm-Malmö rail line.
Trosa is a busy summer resort 60 kilometres south of Stockholm.
SJ trains call at Vagnhärad.
Stockholm Skavsta Airport in Nyköping is the closest passenger airport.
Motorway E4 between Stockholm and Norrköping passes through the municipality.
- Tullgarn Palace
- Tureholm Palace