Highway 99, also known as the Sea to Sky Highway, the Squamish Highway, Route 99, or Whistler Highway, is the major north-south artery running through the Greater Vancouver area of British Columbia from the U.S. border, up Howe Sound through the Sea to Sky Country to Lillooet, and connecting to Highway 97 just north of Cache Creek. The number of this highway is derived from the old U.S. Route 99, with which the highway originally connected. The highway currently connects with Interstate 5 at the international border.

This highway received the '99' designation in 1942 upon completion of the King George Highway, and it originally shared an alignment with Highway 1 from Surrey to Vancouver. The current freeway alignment of Highway 99 between 8th Avenue in South Surrey and the North Arm of the Fraser River opened in 1962. Between 1964 and 1973, the freeway alignment of Highway 99 was designated Highway 499.

In 1957, the northern end of Highway 99 was moved from downtown Vancouver, across the Lions Gate Bridge and west to the village of Horseshoe Bay, following Marine Drive through West Vancouver. Highway 99 was re-aligned via Taylor Way, just east of the Park Royal Shopping Centre, to the Upper Levels Highway and extended to Britannia Beach one year later, extending to Squamish in 1959, and to Pemberton in 1966. Finally, in 1992, the just-paved Duffey Lake Road between Pemberton and Lillooet was made part of Highway 99, and the section of Highway 12 between Lillooet and Highway 97 was re-numbered 99. The portion of the highway between Lillooet and Pavilion was part of the route of the Old Cariboo Road.