The Veteran Reserve Corps (originally the Invalid Corps) was a military reserve organization created within the Union Army during the American Civil War to allow partially disabled or otherwise infirm soldiers (or former soldiers) to perform light duty, freeing non-disabled soldiers to serve on the front lines.

The corps was organized under authority of General Order No. 105, U.S. War Department, dated April 28, 1863. A similar corps had existed in Revolutionary times between 1777 and 1783. The Invalid Corps of the Civil War period was created to make suitable use in a military or semi-military capacity of soldiers who had been rendered unfit for active field service on account of wounds or disease contracted in line of duty, but who were still fit for garrison or other light duty, and were, in the opinion of their commanding officers, meritorious and deserving.

Those serving in the Invalid Corps were divided into two classes:

As the war went on, it proved that the additions to the Corps hardly equaled the losses by discharge or otherwise, so it was finally ordered that the men who had had two years of honorable service in the Union Army or Marine Corps might enlist in the Invalid Corps without regard to disability.

The soldiers shown in the rosters of the 15th Massachusetts Volunteer Infantry Regiment (where they originally enlisted) and who then transferred to the V. R. C. belong to Class 1.

The title "Veteran Reserve Corps" was substituted for that of "Invalid Corps" by General Order No. 111, dated March 18, 1864, to boost the morale as the same initials "I.C." were stamped on condemned property meaning, "Inspected-Condemned". The men serving in the Veteran Reserve Corps were organized into two battalions; the First Battalion including those whose disabilities were comparatively slight and who were still able to handle a musket and do some marching, also to perform guard or provost duty. The Second Battalion was made up of men whose disabilities were more serious, who had perhaps lost limbs or suffered some other grave injury. These latter were commonly employed as cooks, orderlies, nurses, or guards in public buildings.

Invalid Corps members stood out because of their unique uniforms. According to General Orders No. 124, issued May 15, 1863,

The following uniform has been adopted for the Invalid Corps: Jacket: Of sky-blue kersey, with dark-blue trimmings, cut like the jacket of the U.S. Cavalry, to come well down on the loins and abdomen. Trousers: Present regulation, sky-blue. Forage cap: Present regulation.