James Richard Slack (September 28, 1818 – July 28, 1881) was an Indiana politician and a Union general during the American Civil War.

During the Battle of Island Number Ten he commanded the 1st Brigade in General John M. Palmer's 3rd Division of the Army of the Mississippi.

[3] By the end of the war General Slack was in command of the 1st Brigade, 1st Division XIII Corps which he led at the battle of Fort Blakeley.

[3][1] On July 9, 1866, President Andrew Johnson nominated Slack for appointment to the grade of brevet major general of volunteers, to rank from March 13, 1865 and the United States Senate confirmed the appointment on July 23, 1866.

[5] After the war General Slack returned to Huntington to resume his law practice.