Castasegna ([kɐʃtɐˈzeɲɐ]ⓘ) is a former municipality in the district of Maloja in the Swiss canton of Grisons, on the Italian border.

Of the rest of the land, 2.1% is settled (buildings or roads) and the remainder (38.6%) is non-productive (rivers, glaciers or mountains).

In order to relieve the town of the congestion, the highway was moved just below, along the valley floor.

[5] The age distribution, as of 2000[update], in Castasegna is; 20 children or 10.5% of the population are between 0 and 9 years old.

Elektrizitätswerk der Stadt Zürich (EWZ) operates a power plant in Castasegna.

The town's name means chestnut grove and the tree is featured on the coat of arms.