Mitchell & Ness Nostalgia Co. is an American sports-related clothing company located in Philadelphia, Pennsylvania. The company was established in 1904 as a sports equipment manufacturer, remaining as the oldest sporting company in Philadelphia. After several years of making baseball and American football uniforms, the company switched direction in 1983, when it decided to recreate vintage jerseys.

Nowadays, Mitchell & Ness has license agreements with five of the major sports leagues of the United States (MLB, NBA, NFL, NHL, and MLS) to produce and commercialise vintage sports equipment and casual wear.

Some of Mitchell & Ness products include team uniforms (jerseys and shorts) and other casual wear such as t-shirts, tracksuits, jackets, hoodies, hats, knit caps, and other accessories (pennants). The company also has its own brand, "M&N".

In February 2022, Mitchell & Ness was acquired by Fanatics, Inc., along with a group of investors including LeBron James, Jay-Z, and Kevin Hart.

Frank P. Mitchell, a former Amateur Athletic Union tennis and wrestling champion, and Charles M. Ness, an avid golfer born in Scotland, together founded "Mitchell & Ness Sporting Goods" in 1904. Their original store made and strung hand-crafted tennis rackets and, using imported woods from Scotland, stolen from England, constructed custom-made golf clubs. In time, they expanded their business, selling uniforms to local baseball and American football teams. When the Philadelphia Eagles entered the young National Football League (NFL) in 1933, Mitchell & Ness supplied the team jerseys and equipment. Mitchell & Ness would continue to outfit the Eagles through the 1963 season.

The first time that the Mitchell & Ness label appeared on a major league baseball uniform, the Philadelphia Athletics, was in 1938. In the early 1940s, Mitchell & Ness began to supply Philadelphia's other major league baseball team, the Phillies. By the end of the decade, the Mitchell & Ness label was appearing on high school and college team uniforms throughout the Philadelphia area.

In the late 1970s, Mitchell & Ness had dropped the team business to concentrate on its retail operation. The store became a leading outlet for field hockey equipment and ski gear. Mitchell & Ness almost went bankrupt in 1983. Owner Peter Capolino told the Detroit Free Press, "By 1983 all the expansion I had done had gone to hell. I fired 100 people, closed two warehouses. I reduced the company to a little store at 13th and Walnut Streets (in Philadelphia). It was down to just me and my wife."

In 1983, a customer walked into the store and asked if Mitchell & Ness could repair his 1960 Pittsburgh Pirates game-worn vest, and his 1949 St. Louis Browns game-worn shirt. They were both made of wool flannel as all baseball uniforms had been during that era. Mitchell & Ness found that it could do it, and with the realization that Mitchell & Ness was capable of this task, an idea was born: Reproduce historically accurate wool-flannel baseball uniforms. Mitchell & Ness recruited history buffs and sports gurus most notably Capolino's friend Bob Downes. They dug through old newspapers, periodicals, books, programs, and old film footage. They consulted vintage uniform collectors throughout the country and visited the archives at the Baseball Hall of Fame in Cooperstown, New York.