Irgenhausen Castrum is a Roman fort at Irgenhausen, situated on Pfäffikersee lake shore in Switzerland . It was a square fort, measuring 60 metres (197 ft) in square, with four corner towers and three additional towers. The remains of a stone wall in the interior were probably a spa.

The castrum is situated on the Bürglen hill in Irgenhausen, a village of the municipality of Pfäffikon in the canton of Zürich in Switzerland. Bürglen (Swiss German: "small castle") is a 25 metres (82 ft) high drumlin, 400 metres (1,312 ft) from the eastern shore of Pfäffikersee, situated between Pfäffikon and Kempten, the site of another Roman settlement nearby.

In the Roman era, along Pfäffikersee there was a Roman road from Centum Prata (Kempraten ) on Obersee–Lake Zürich via Vitudurum (Oberwinterthur ) to Tasgetium (Eschenz ) on the Rhine.