Steiria (Ancient Greek: Στείρια) was a deme of ancient Athens on the east coast, between Prasiae and Brauron. Stiris in Phocis is said to have been founded by the inhabitants of this deme. The road from Athens to Steiria and the harbour of Prasiae was called the Στειριακὴ ὁδός. Steiria was the deme of Theramenes and Thrasybulus.
Steiria is located west of Porto Rafti.