Patrick Kelly (ca. 1822 – June 14, 1864) was an Irish-American Union Army officer in during the American Civil War. He led the famed Irish Brigade at the Battle of Gettysburg.

Kelly was born in Castlehacket, County Galway, Ireland, and emigrated to the United States of America, landing in New York City. His wife Elizabeth was another Irish immigrant. He enlisted in the Union army with the outset of the Civil War, and saw action as captain of Company E of the 69th New York Infantry at the First Battle of Bull Run. He briefly was a captain in the 16th U.S. Infantry. On September 14, 1861, he was named lieutenant colonel of the 88th New York Infantry and fought in the Irish Brigade's major battles in 1862. He commanded the regiment at the Battle of Antietam. While stationed at Harpers Ferry following the Maryland Campaign, he was promoted to colonel on October 20, 1862. He led the regiment in the ill-fated attacks in front of Marye's Heights in the Battle of Fredericksburg. Col Kelly was acting commander of the Irish Brigade at the end of 1862.

After the 1863 Battle of Chancellorsville, Kelly was promoted to command the Irish Brigade following the resignation of Brig. Gen. Thomas Meagher. Kelly led the heavily depleted brigade (down to less than 600 men) in an attack at the Wheatfield at Gettysburg. The brigade lost 198 of 532 troops engaged (ca. 37%).