The Seafair Cup (branded as the HomeStreet Bank Cup for sponsorship reasons, and formerly the Albert Lee Appliance Cup), is an H1 Unlimited hydroplane boat race held annually in late July and early August on Lake Washington in Seattle, Washington.

Seattle's history of unlimited hydroplane racing dates back to July 1950, when it was announced that the APBA Gold Cup was leaving Detroit in favor of Seattle.

Slo-mo-shun IV, owned by Stanley Sayres, won the Gold Cup race in Detroit that year.

Greater Seattle, Inc. (later renamed Seafair, Inc.) became the sole sponsor of the race, starting in 1961.

[2] Lou Fageol won the very first Seattle race driving Stan Sayres' Slo-mo-shun V.[3] The Emerald City has hosted the Unlimiteds every year from 1951 to 2019.