James William Forsyth (August 8, 1834 – October 24, 1906) was a U.S. Army officer and general. He was primarily a Union staff officer during the American Civil War and cavalry regimental commander during the American Indian Wars. Forsyth is best known for having commanded the 7th Cavalry at the Wounded Knee Massacre on December 29, 1890, during which more than 250 men, women, and children of the Lakota were killed and more than 50 were wounded.

Forsyth was born in Maumee, Ohio, where he attended the local schools. He attended West Point from 1851 to 1856 and received a commission as second lieutenant in Co. D, 9th U.S. Infantry. He was instrumental in the completion of the frontier fort at San Juan Island and served as the company's acting commander when Captain George E. Pickett was away on leave. After serving in Washington Territory at Fort Bellingham and Camp Pickett, San Juan Island, Forsyth was promoted to first lieutenant in 1861 and returned to the East to command Union forces in the Civil War.

Forsyth joined the Union Army as Colonel of the 64th Ohio Infantry on November 9, 1861. He was temporarily in command of a brigade during Don Carlos Buell's march to the relief of Maj. Gen. U.S. Grant at Shiloh. However, the day before the battle began the brigade's regular commander, James A. Garfield, returned and Forsyth did not participate in the actual battle. Forsyth relinquished command of the 64th Ohio to Colonel John Ferguson on 1 January 1862.

In 1862, he transferred to the Army of the Potomac where he served as the assistant U.S. inspector general during the Peninsula campaign. During the Maryland Campaign, he was assigned as aide-de-camp to Major General Joseph K. F. Mansfield until the latter's untimely death at the Battle of Antietam. Forsyth then became provost marshal to the Army of the Potomac at the Battle of Fredericksburg.

In 1863, Forsyth transferred back to the Western Theater to serve as adjutant to General Philip H. Sheridan at Chickamauga. Forsyth was brevetted to Major in the Regular Army for his service at Chickamauga. When Sheridan transferred to the Army of the Potomac's Cavalry Corps, Forsyth followed as his chief of staff. He participated in this capacity during the Overland Campaign. He was subsequently chief of staff of the Army of the Shenandoah during the Shenandoah Valley Campaign of 1864 and chief of staff to the Union Cavalries during the Appomattox Campaign. He received brevets to Lieutenant Colonel, USA for Cedar Creek, colonel, USA for Five Forks and Brigadier General, U.S. Volunteers, for the Shenandoah Valley Campaign.

On January 13, 1866, President Andrew Johnson promoted Forsyth to Brigadier General of Volunteers to rank from May 19, 1865. The U.S. Senate confirmed the appointment on February 23, 1866, notwithstanding that Forsyth was mustered out of the volunteer service on January 15, 1866. On July 17, 1866, President Johnson nominated Forsyth for appointment as a brevet Brigadier General in the regular army to rank from April 9, 1865. The Senate confirmed the appointment on July 23, 1866.

Forsyth served under Sheridan along with Wesley Merritt, Thomas Devin, and George A. Custer. Later, all of these men would become famous Indian fighters.

After the war, Forsyth was elected as a veteran companion of the first class of the Illinois Commandery of the Military Order of the Loyal Legion of the United States.