Dunbar R. Ransom (January 10, 1831 – July 11, 1897) was a United States Army officer and veteran of the American Civil War.

Ransom participated in the later stages of the Yakima War in an expedition during 1858 that culminated in the Battle of Four Lakes near Spokane, Washington.

[7] Ransom's battery remained with the Reserves when they joined I Corps of the Army of the Potomac in time for the Battle of Antietam.

Maj. Gen. George G. Meade, who led the division at Antietam, praised Ransom's battery for its support of the Reserves as they advanced into and beyond the Cornfield.

[13] The batteries of Thomas, Weir, and Trumbull all served on Cemetery Ridge during the Confederate bombardment and unsuccessful assault on July 3.

[15] After returning to the Army of the Potomac with Battery C, Ransom was assigned to the 2nd brigade of Horse Artillery under William M. Graham.

In 1872 Ransom was charged with conduct unbecoming an officer for having borrowed money to facilitate travel from one military assignment to another, and resorting to deceit to avoid repaying it, and he was dismissed from the service.

Later he was aided by Grenville M. Dodge, the president of the railroad, who brought the matter of Ransom's dismissal to the attention of Congress.

In 1892 a Congressional investigation determined that Ransom had not been deceitful, that his Army pay had been delayed for more than a year because of his travel between posts at the time of the loan, and that he had not intentionally avoided repaying the debt.

Further, Congress determined that even if Ransom had intentionally tried to avoid repaying the debt, that would have been a private matter and not professional conduct unbecoming an officer.

In 1894 Congress restored Ransom to the Army's rolls and transferred him to the retired list, enabling him to qualify for a pension.