The 51st New York Infantry Regiment (or Shepard Rifles) was an infantry regiment in the Union Army during the American Civil War.

The regiment was attached to Reno's 2nd Brigade, Burnside's North Carolina Expeditionary Corps, to April 1862.

2nd Brigade, 2nd Division, Department of North Carolina, to July 1862.

2nd Brigade, 2nd Division, IX Corps, Army of the Potomac, to April 1863.

District of North Central Kentucky, 1st Division, XXIII Corps, Army of the Ohio, to February 1864.

2nd Brigade, 2nd Division, IX Corps, Army of the Potomac, to April 1864.

1st Brigade, 2nd Division, IX Corps, Army of the Potomac, to May 26, 1864.

1st Brigade, 2nd Division, IX Corps, to July 1865.

The 51st New York Infantry mustered out of service on July 25, 1865.

Burnside's Expedition to Hatteras Inlet and Roanoke, Island, N.C., January 6-February 7, 1862.

Moved to Newport News, Va., July 6–9, then to Fredericksburg August 2–4.

Moved to Newport News, Va., February 19, then to Covington and Paris, Ky., March 26-April 1.

Sterling, Ky., April 3, to Lancaster May 6–7, and to Crab Orchard May 23.

Poplar Grove Church, Peeble's Farm September 29-October 2.

Boydton Plank Road, Hatcher's Run, October 27–28.

Moved to Petersburg, then to City Point and Washington, D.C., April 20–28.