Charles "The Ox" Reiser (1878-October 10, 1921) was a safecracker as well as a mentor to many of the organized crime leaders of the early 20th Century including Dion O'Banion, George Bugs Moran, Hymie Weiss, and John Mahoney.

Born in 1878 little is known of Reisers early life however he was first arrested in 1902 and charged with safecracking. While released on bail however he reportedly killed the witness testifing against him and the case was subsequently dropped. Two years later he was arrested in 1905 and again the case was dropped after another witness disappeared. In 1907 he was convicted of assault with a deadly weapon and sentenced to 30 days. In 1909 Reiser was apprehended in Seattle, Washington and charged with burglary and murder yet, as in Chicago, the witnesses against him were killed and Reiser returned to Chicago shortly after.

Around 1914 Reiser met Dion O'Banion who, along with several of his friends, would later accompany him in several safecraking jobs. During this time, while living under the alias Charles Shopes, he would use most of his money gained from robbery investing it into real estate eventually becoming the owner of a large apartment building and later remarried shortly after. His first wife had previously died of asphyxiation although Raiser had allegedly bragged to friends he had beaten her to death after she threatened to turn him in to the police.

In 1920 Raiser killed partner Clarance White , who had contacted Raiser that Chicago police had called him in for questioning regarding the robbery of a Standard Oil Co. safe which he and White had stolen, making it appear White had committed suicide. John Mahoney, who had been arrested while safecracking himself, reported this to the police as well as additional information however he was also murdered by Raiser in April 1921.

While recovering in a Chicago hospital after an attempted robbery he apparently committed suicide, shot over 10 times, after a visit from his wife. While Raiser's wife was charged with the suspicious death the case was later dropped.