Harry Chesler (January 12, 1897, or January 12, 1898 (sources differ) – December 29, 1981), often credited as Harry "A" Chesler, with the "A" an affectation rather than a true initial, was the entrepreneur behind the first comic book packager of the late-1930s to 1940s Golden Age of comic books, supplying comics features and complete comic books to publishers testing the waters of the emerging medium.

Chesler's studio, which began in either 1935 or 1936, provided early work to artists and writers including Jack Cole, Jack Binder, Otto Binder, Charles Biro, Mort Meskin, and many others.

Chesler was born either in Kaunas, Vilna Governorate on January 12, 1897, or, as given by his United States Social Security data, on January 12, 1898, in Jersey City, New Jersey. One source gives his birth name as Aaron Czesler, nicknamed Ari, the phonetic equivalent of Harry. That source says his parents, who were Jewish, married in 1895 and had two other children, Lena (b. 1896) and Sadie (b. 1900); the family immigrated to the U.S. in 1903, changing their name to Chesler.

Most often credited as Harry "A" Chesler — the "A" was an affectation rather than a true initial, and Chesler sometimes quipped it stood for "anything" — Chesler grew up in East Orange, New Jersey where he graduated from East Orange High School in June 1915. He worked in his father's grocery and in the furniture business. He moved with his family to The Bronx, New York City in 1917. There his father bought a grocery wholesale firm at 1493 Zerega Avenue, with the family living nearby at 2903 Lyon Avenue. Harry Chesler registered for the draft on September 12, 1918, and served as a U.S. Army private during World War I.

In 1919, after his discharge, Chesler returned to New Jersey, where he sold ads for The Jersey Journal and lived at 1463 East 100th Street in Jersey City. He also worked for a time at the Philadelphia Public Ledger, where he picked up his fictitious middle initial. By April 1923, he owned the outdoor advertising firm the Harry "A" Chesler Company of 15 Beecher Street in Newark, New Jersey. In 1928, he bought a 90-acre summer-home property in the Succasunna section of Roxbury Township, New Jersey, and opened a side-business dairy store. He would later live in Succasunna full-time.

In 1935 or 1936, Chesler established a studio in Manhattan to supply comic-book content to publishers testing the waters of the emerging medium. The "Chesler shop", as it was informally called, was the first such "packager", later to be followed by companies including Eisner & Iger and Funnies Inc. Chesler in 1976 recalled it was located first at Fifth Avenue and 32nd Street, and later at Seventh Avenue and 23rd Street. George Tuska, a comic-book artist who had worked for Chesler in the late 1930s, recalled, "Chelser had his office on the fourth floor of a building on 23rd Street between Sixth and Seventh Avenue[s]". (One source lists the studio at 28th Street and Fifth Avenue.) During this time, Chesler commuted from his home in Dover, New Jersey.

Chesler's early publications Star Comics and Star Ranger were produced through his own Chesler Publications, Inc. These were bought by Ultem Publications in 1937, where he continued as editor until Ultem was in turn bought by Centaur Publications in 1938. By the late 1930s, Chesler's packaging business was flourishing. As Tuska recalled, Chesler "did alright with comics. Bought a lot of property in Jersey. Made his own lake".

Chesler employees remembered him as a tough but warm boss who always wore a hat and smoked a big cigar. Artist Joe Kubert recalled Chesler paying him $5 a week, at age 12 (c. 1938) to apprentice at his studio after school. Similarly, artist Carmine Infantino remembers that, c. 1940, he was paid by Chesler "a dollar a day, just [to] study art, learn, and grow. That was damn nice of him, I thought. He did that for me for a whole summer" while Infantino was in high school.