Patrick Henry O'Rorke or O'Rourke[1] (March 25, 1837 – July 2, 1863) was an Irish-American immigrant who became a colonel in the Union Army during the American Civil War and was killed at the Battle of Gettysburg.

[4] In 1853, at age 16, he was awarded a scholarship to the University of Rochester; however, before attending college, his father died, and O'Rorke, to support his family, took a job as a marble cutter at the request of his mother.

[6] In July 1861, O'Rorke served at the Battle of Blackburn's Ford and the First Battle of Bull Run, where his horse was killed from under him, and then as assistant engineer in preparing the defenses of Washington, D.C.[3][6][7] He sailed with the Port Royal Expedition[6][8] in October 1861 and provided vital reconnaissance[9] and engineering in constructing the batteries on Jones,[10] Bird,[11] and Tybee Islands for the bombardment and siege of Fort Pulaski, on Cockspur Island near Savannah, Georgia.

[12][13] In September 1862, O'Rorke was appointed colonel of the 140th New York Infantry which was composed mostly of volunteers from his hometown of Rochester and heavily of fellow Irish-Americans.

Gen. Gouverneur K. Warren was desperately searching for units to defend Little Round Top, and he encountered O'Rorke's New Yorkers, the rearmost regiment in Weed's brigade, on their way to reinforce the III Corps.

"[14] O'Rorke rushed his men to the crest of the hill and plunged down its western face without pause, driving the attacking Confederates back down the slope.

[13] A funeral for Colonel O'Rorke was held on July 15 in Rochester drawing hundreds of attendees, both Catholic and Protestant and across a range of ethnic groups.