The Ohio Army National Guard is a part of the Ohio National Guard and the Army National Guard of the United States Army. It is also a component of the organized militia of the state of Ohio, which also includes the Ohio Naval Militia, the Ohio Military Reserve and the Ohio Air National Guard. The Ohio Army National Guard consists of a variety of combat, combat support and combat service support units. As of September 2010, its end strength exceeded 11,400 soldiers. Its headquarters is the Beightler Armory in Columbus, Ohio. Many units conduct Annual Training at Camp Grayling, Michigan.

On May 4, 1970, Guard units infamously opened fire onto a crowd of both Vietnam War protestors and simple bystanders on the campus of Kent State University, killing four and wounding nine others, an event known as the Kent State shootings. The President's Commission on Campus Unrest concluded that the Guard's actions were "unnecessary, unwarranted, and inexcusable."