Interstate 465 (I-465), also known as the USS Indianapolis Memorial Highway, is the beltway circling Indianapolis, Indiana, United States. It is roughly rectangular in shape and has a perimeter of approximately 53 miles (85 km). It lies almost completely within the boundaries of Marion County, except for two short sections on the north leg in Boone and Hamilton Counties. It crosses I-65, I-69, I-70 and I-74, and provides additional access to I-65 via I-865. An $800 million project is underway to refurbish the western edge of the loop, with an estimated completion in the fall of 2012.

Except for I-65 and I-70, no numbered highways run through downtown Indianapolis. All highways that continue from one side to the other are routed around the city, concurrent with I-465:

The approximately one-mile section between exits 46 and 47 carries eight routes â€” I-465, US 31, US 36, US 40, US 52, US 421, SR 37 and SR 67. It may also carry Interstate 69 in the future.

In most cases, markers other than I-74's are not posted along I-465 itself; rather, signs on the onramps direct traffic following a particular route to follow I-465 to a particular exit to continue on that route.

Much of I-465 replaced the routing of the defunct parallel State Road 100.

In 2002, the Interstate 865 designation was created from a portion of I-465 to eliminate the three-way intersection of I-465.

Also in 2002, Indianapolis native David Letterman's late-night talk show sidekick and band leader Paul Shaffer was honored by having a street in Thunder Bay, Ontario, named for him. This led Letterman to ask (on his program) why he couldn't have his own eponymous road, and he suggested I-465 be named the David Letterman Expressway. His fans took the idea seriously, especially in the Indianapolis area where highway signs promoting the idea were displayed. Advertisers and traffic reports started to refer to I-465 as the "DLX", or later the "David Letterman Bypass", a reference to his quintuple heart bypass surgery in January 2000. Letterman even telephoned the Mayor of Indianapolis, Bart Peterson to make his case, but eventually the idea went nowhere.

In 2011 the Indiana General Assembly passed a resolution naming I-465 as "USS Indianapolis Memorial Highway" in "the memory of the brave sailors who lost their lives" when USS Indianapolis was sunk in the Pacific during World War II.

Eventually, Interstate 69 will run concurrent with Interstate 465 clockwise around Indianapolis from the current south end to somewhere between exits for State Road 37 and State Road 67 on the south side.