Treasure Island Causeway, Road bridge in Pinellas County, US.

Treasure Island Causeway is a series of three bridges across Boca Ciega Bay between Treasure Island and St. Petersburg in Pinellas County, Florida, carrying County Road 150. The outer two spans are fixed; the middle span is a bascule drawbridge. The causeway is owned and maintained by the City of Treasure Island, and its western terminus meets Gulf of Mexico Boulevard (SR 699) in Treasure Island.

The causeway opened to traffic in 1939 as a toll route to the Pinellas County barrier islands. A 2002 engineering study found all three bridges structurally deficient; the west and east spans were rebuilt between late 2003 and October 2004. The drawbridge closed on 3 January 2006, one leaf reopened on 10 June 2006, and the finished causeway was dedicated on 25 August 2007. The $1.00 toll ended in 2006 when the first span reopened without a toll booth.

The causeway links the mainland to barrier islands and serves as the primary route for residents and visitors heading to Gulf Coast beaches. People naturally use it as a gateway between urban areas and the quieter seaside communities.

The causeway carries County Road 150 from Gulf of Mexico Boulevard (SR 699) in Treasure Island east to St. Petersburg. Its middle span is a bascule drawbridge that opens for boats, so drivers can face short waits there. The drawbridge was closed for replacement from January 3, 2006, and one leaf reopened to vehicles on June 10, 2006.

Despite being located within St. Petersburg city limits, the causeway is owned and operated by the City of Treasure Island through an early municipal agreement. This unusual arrangement allows a smaller coastal community to manage a major transportation link.