Indiana State Road 431

State highway in Indiana, United States

State Road 431 was a state road connecting U. S. Route 31 with Interstate 465 at Exit 33. It passed through the Indianapolis suburb of Carmel, allowing traffic on U. S. 31 north of Carmel a shorter route to I 465 and the east side of Indianapolis. Until the 1990s, the SR 431 designation extended south of I 465 to 86th Street. Prior to that, it also continued south along N. Keystone Avenue to State Road 37 at Fall Creek Parkway, North Drive in Indianapolis. A second section of SR 431 followed the old route of U. S. 31 between Greenwood and the south side of Indianapolis.

Beginning at a junction with US 31 in Greenwood, SR 431 traveled along Madison Avenue northwest to the south side of Indianapolis. On Madison Avenue, SR 431 passed through a mix of residential and commercial properties. The suburban surroundings dominated much of the route until it began to encroach on the outskirts of Indianapolis. The highway terminated at US 31, now S. East Street, in Indianapolis. Carmel Mayor James Brainard immediately proposed banning heavy trucks from the route, the Hamilton County portion of which lies within his city's corporate limits. At this point, the street name was changed from Keystone Avenue (a designation that remains south of the county line at 96th Street in Indianapolis) to Keystone Parkway. Brainard also pushed for a plan to build six roundabout style ("dogbone") interchanges on Keystone, built 2009–2010, in lieu of widening it to at least six travel lanes throughout. On December 30, 2019, another such interchange was opened at the junction with 96th Street.