Amos Urban Shirk (1890? – October 20, 1956) was an American businessman, author and reader of encyclopedias.
As a businessman he worked in the food industry. He wrote Marketing Through Food Brokers, published in 1939 by McGraw-Hill. He invented a synthetic chicle and introduced vitamin capsules to grocery stores.
He was also renowned as a prodigious reader. Shirk read the entire 23-volume 1911 Encyclopædia Britannica from cover to cover in four and a half years, reading on average 3 hours per evening, and taking two to six months per volume. As of 1938 he had begun reading the 14th edition, saying he found it a "big improvement" over the 11th, and saying that "most of the material had been completely rewritten".
Shirk did not limit himself to Britannica. He also read Henry Smith Williams's 24-volume Historians' History of the World, which took him two years. Among his other feats of prodigious reading were an eighteen-volume set of Dumas (read twice), a thirty-two-volume set of Balzac (twice), and a twenty-volume set of Charles Dickens (three times).
Shirk had other hobbies including painting and record collecting.