To provide a surgical stapling device having a rotatable stapling head for applying staples to tissue, particularly, a new surgical stapling device having a locking mechanism for preventing the rotation of the stapling head.

A surgical stapling device 10' includes: a housing; an actuation member; an elongated body portion rotatably supported on the housing; and a locking mechanism for preventing the rotation of the elongated body portion, the locking mechanism being automatically engaged upon actuation of the actuation member. The elongated body portion includes a knob for rotating the elongated body portion. The locking mechanism may include a pivotably mounted member configured to engage the knob 32'. The surgical stapling device further may include an articuable tool assembly 20'.