Clarence Leonard "Kelly" Johnson (February 27, 1910 – December 21, 1990) was an American aeronautical and systems engineer. He is recognized for his contributions to a series of important aircraft designs, most notably the Lockheed U-2 and SR-71 Blackbird. Besides the first production aircraft to exceed Mach 3, he also produced the first fighter capable of Mach 2, the United States' first operational jet fighter, as well as the first fighter to exceed 400 mph, and many other contributions to various aircraft.

As a member and first team leader of the Lockheed Skunk Works, Johnson worked for more than four decades and is said to have been an "organizing genius". He played a leading role in the design of over forty aircraft, including several honored with the prestigious Collier Trophy, acquiring a reputation as one of the most talented and prolific aircraft design engineers in the history of aviation.

In 2003, as part of its commemoration of the 100th anniversary of the Wright Brothers' flight, Aviation Week & Space Technology ranked Johnson eighth on its list of the top 100 "most important, most interesting, and most influential people" in the first century of aerospace. Hall Hibbard, Johnson's Lockheed boss, referring to Johnson's Swedish ancestry, once remarked to Ben Rich: "That damned Swede can actually see air."

Kelly Johnson was born in the remote mining town of Ishpeming, Michigan. His parents were Swedish, from the city of Malmö, county of Scania. His father ran a construction company. Johnson was 13 years old when he won a prize for his first aircraft design. He attended Flint Central High School and graduated in 1928, then went to Flint Junior College, now known as Mott Community College, and finally to the University of Michigan in Ann Arbor, where he received a Bachelor's and Master's Degree in Aeronautical Engineering.

While attending grade school in Michigan, he was ridiculed for his name, Clarence. Some boys started calling him "Clara". One morning while waiting in line to get into a classroom, one boy started with the normal routine of calling him "Clara". Johnson tripped him so hard the boy broke a leg. The boys then decided that he was not a "Clara" after all, and started calling him "Kelly". The nickname came from the popular song at the time, "Has Anyone Here Seen Kelly? (Kelly from the Emerald Isle)". Henceforth, he was always known as "Kelly" Johnson.

In 1937, Johnson married Althea Louise Young, who worked in Lockheed's accounting department; she died in December 1969.

In May 1971, he married his secretary Maryellen Elberta Meade of New York; she died after a long illness on October 13, 1980, aged 46.

He married Meade's friend Nancy Powers Horrigan in November 1980.^{[citation needed]}