Harrisburg International Airport or KMDT is a public airport in Middletown, Pennsylvania just southeast of Harrisburg. It is owned by the Susquehanna Area Regional Airport Authority.

The airport code MDT refers to Middletown, the town in which the airport is located. Planes landing at MDT from the south are often routed near Three Mile Island Nuclear Generating Station a few miles from the airport.

KMDT started off as a duty post of US Army Signal Corps troops in 1898 and saw its first aircraft land in 1918 after it had became known as Olmsted field and home to the US Army Air Service.