Interstate 275 (I-275) is an 83.71-mile-long (134.72 km) loop in Ohio, Indiana, and Kentucky that forms a complete beltway around the Cincinnati, Ohio, area. It is the only auxiliary interstate that enters three states, including one state that the parent route does not enter (Indiana). It is the longest loop interstate highway in the United States. For a short distance in northwest Hamilton County it overlaps with I-74 and U.S. Highway 52 (US 52).

I-275 is signed as the "Cincinnati By-Pass" and officially known as the Donald H. Rolf Circle Freeway in Ohio, after a state senator, but locals rarely use these names, instead simply referring to it as "two-seventy-five." In 2011, Kentucky named its segment the Ronald Reagan Highway. The section in Clermont County is also designated as the Staff Sergeant Matt Maupin Veterans Memorial Highway.

I-275 heads west toward Indiana passing by the Cincinnati/Northern Kentucky International Airport, with Kentucky Route 212 (KY 212) used as the service road to and from the airport.  Then near Hebron, west of the airport, I-275 has an interchange with Kentucky Route 237 (KY 237), before passing over the Ohio River into Indiana.

In Indiana I-275 passes through rural area with only one interchange and it is at U.S. Route 50 (US 50)/State Road 1 (SR 1).  I-275 heads northeast towards Ohio, at the Ohio state line I-275 passes over US 50.

I-275 heads northeast towards Springdale.  I-275 has a short concurrency with Interstate 74 (I-74).  When the concurrency ends, I-275 has an intersection with Ohio State Route 126 (Ronald Reagan Cross County Highway).  Then I-275 has an interchanges with U.S. Route 27 (US 27) and U.S. Route 127 (US 127).  I-275 turns east having an interchange with State Route 4, State Route 747, Interstate 75, and U.S. Route 42.  I-275 turns southeast having an interchange with Interstate 71 and U.S. Route 22.  I-275 passes through over the Little Miami River and I-275 turns due south toward Milford.  I-275 then has interchanges with State Route 28, State Route 450, State Route 32, and State Road 125.  I-275 turns due west towards Kentucky, passing through a short concurrency with U.S. Route 52 (US 52), before crossing over the Ohio River into Kentucky.

From Ohio I-275 heads southwest towards Highland Heights.  I-275 has an interchange with Interstate 471 (I-471) near Highland Heights.  I-275 turns due west towards Crestview Hills, passing through an interchange with Kentucky Route 9 (KY 9), Kentucky Route 16 (KY 16), and Kentucky Route 17 (KY 17).  In Crestview Hills I-275 has an interchange with U.S. Route 25/U.S. Route 42/U.S. Route 127.  I-275 turns northeast towards Interstate 71/Interstate 75.

On May 20, 2008, a tractor-trailer hauling a locomotive separated while traveling on the ramp from westbound I-74 to southbound I-275. After the trailer detached, it crashed into supports for the bridge on I-74 eastbound going over the ramps between I-275 and I-74 westbound. As a result, the Ohio Department of Transportation shut down eastbound I-74 for several weeks. Both ramps between I-74 west and I-275 were closed as well, because of fears the bridge would collapse, but two crossovers were built so that traffic could use one lane of westbound I-74 to travel east around the damaged bridge.