Brithombar, along with Eglarest, was one to the two great havens built in Beleriand during the Years of the Trees. It stood at the mouth of the River Brithon.

Brithombar was fortified after the return of Morgoth, but eventually fell along with Eglarest late in the First Age, when the Noldor lost control of the northern regions of Beleriand and the forces of Morgoth were able to establish control further south.