'IB' was a British naval minelaying operation off the island of Heligoland in the German Bight (17/18 December 1939).

The destroyers Intrepid and Ivanhoe laid a field of 240 mines off Borkum in the mouth of the Ems river, and the operation was covered by the destroyers Grenville, Greyhound, Griffin and Polish Błyskawica. After the field had been laid, the Harwich-based covering destroyers carried out a anti-submarine sweep and arrived back at Harwich by dusk.