达西安镰刀（Falx）是达西安人（Dacian）使用的一种双手武器。达西安镰刀的刀身往内弯曲，在内侧有刀锋，并有不短的木制把手，适合劈、砍、扯等动作。

Falx is a Latin word originally meaning sickle but was later used to mean any of a number of tools that had a curved blade that was sharp on the inside edge such as a scythe. Falx was also used to mean a weapon – particularly that of the Thracians and Dacians – and, later, a siege hook used by the Romans themselves.