The Sixth Street Bridge is a four-span, wrought iron bridge that crosses the Grand River in Grand Rapids, Michigan. It is a Michigan State Historic Site and is listed on the National Register of Historic Places.

The Bridge Marker is located at the intersection of 6th Street Northwest and Monroe Avenue Northwest, on the right when traveling east on 6th Street Northwest.

The Massillon Bridge Company of Ohio built The Sixth Street Bridge $31,000, four-span, bridge for Grand Rapids in 1886.

The piers and abutments are masonry and built of local Grand River limestone.

It is the longest and oldest metal truss bridge in Michigan. It is also the longest pin-connected highway truss in the state of Michigan. Michigan only has a few truss bridges that are more than one span in length, and most of those are two spans.

A four-span bridge in Michigan is thus extremely rare for its unusually long length and the rust-resistant wrought iron used in its four Pratt trusses accounts for its durability.

In 1921 the western truss was shortened when the west bank canal was filled in. In 1975 the bridge was slated for demolition, but concerned citizens convinced authorities to save it. This structure, the longest, oldest remaining metal bridge in Michigan, was listed in the National Register of Historic Places in 1976.