Kachemak Bay (Dena'ina: Tika Kaq’) is a 40-mi-long (64 km) arm of Cook Inlet in the U.S. state of Alaska, located on the southwest side of the Kenai Peninsula.

The communities of Homer, Halibut Cove, Seldovia, Nanwalek, Port Graham, and Kachemak City are on the bay as well as three Old Believer settlements in the Fox River area, Voznesenka, Kachemak Selo, and Razdolna.

The bay provides winter homes for 90% of the seabird and waterfowl populations of Lower Cook Inlet.

The tides at Kachemak Bay are extreme, with an average vertical difference (also called mean range) of 15.53 ft (4.73 m), and recorded extremes of 31.72 ft (9.67 m) as measured at the Seldovia Tide Station.

The highest tide on record is 25.25 ft (7.70 m) above MLLW (mean lower low water) and occurred on November 15, 1966.