The Siege of Macindaw is the sixth book in the Ranger's Apprentice series by Australian author John Flanagan.

With the overthrow of Castle Macindaw by Keren, Orman's traitorous cousin, Will needs to find men to help win back the crucial northern stronghold.

Halt and Crowley, Will's former mentor and the leader of the Ranger Corps, send the young knight Horace to help Will.

The castle defenders quickly become uninterested in the strange machine and are easily distracted by a show of lights to the south, caused by Will's ally, the "sorcerer" Malcolm.

They slaughter the defenders and quickly gain a foothold in the castle and Will runs to the central tower to rescue Alyss.