USCGC Mackinaw (WLBB-30) is a 240-foot (73 m) vessel built as a heavy icebreaker for operations on the North American Great Lakes for the United States Coast Guard. IMO number: 9271054. She should not be confused with a namesake ship, the USCGC Mackinaw (WAGB-83), IMO number: IMO 6119534, which was decommissioned on June 10, 2006.

Mackinaw was delivered to the Coast Guard on November 18, 2005 and commissioned on June 10, 2006. In addition to her ice-breaking duties, the Mackinaw will also serve as an Aids to Navigation ship, able to perform the same duties as the Seagoing Buoy Tenders (WLB) of the Coast Guard fleet.

Commissioned: June 10, 2006
Homeport: Cheboygan MI
Displacement: 3,500 tons
Length: 240 ft (73 m)
Beam: 58.5 ft (17.8 m)
Draft: 16 ft (4.9 m)