Robertson County is a county located on the central northern border of Tennessee in the United States. As of the 2020 United States census, the population was 72,803. Its seat of government is Springfield. The county was named for James Robertson, an explorer, founder of Nashville, and a state senator, who was often called the "Father of Middle Tennessee." Robertson County is a component of the Nashville-Davidson–Murfreesboro–Franklin, TN Metropolitan Statistical Area.

This was part of the Miro District (also spelled Mero), named after the Spanish Governor Esteban Rodríguez Miró of what was then Louisiana on the west side of the Mississippi River. Miró had served with Spanish troops that assisted the Americans during their war for independence. James Robertson, the explorer for whom this county was named, was trying to create an alliance with Miró that would allow free movement on the Mississippi River (which Spain controlled) to settlers on the Cumberland frontier. Before statehood, this territory was known as Tennessee County.

Thomas Kilgore, the first European settler in Robertson County, arrived in 1778 to establish a settlement in what is now present-day Cross Plains. Robertson County was organized in 1796, at the same time as Montgomery County, which had also been part of the Miro district. The county seat, Springfield, Tennessee, was laid out in 1798. Although initially, most settlers did not hold slaves, by the 1820s planters began to cultivate tobacco, a commodity crop that was labor-intensive and depended on enslaved African Americans. The planters bought slaves to work their plantations, as well as to care for the livestock they bred - thoroughbred horses and cattle.

By the time of the Civil War, African Americans comprised about one-quarter of the area's population, typical for Middle Tennessee, where tobacco and hemp were commodity crops. During the Civil War, Tennessee was occupied by the Union from 1862, which led to a breakdown in social organization in Middle Tennessee.

By 1910 the county's population was 25,466, including 6,492 black citizens, who continued to make up one-quarter of the total. Most of the residents were still involved in farm work, and tobacco was the primary commodity crop, but agricultural mechanization was reducing the need for laborers. White Democrats had tried to restrict black voting; other southern states had excluded blacks from the political process. Many African Americans left rural Robertson County and other parts of Tennessee in the Great Migration to northern and midwestern cities for employment and social freedom. Combined with the later in-migration of whites to the county, by the early 21st century, African Americans comprised less than 10 percent of the county population. They live chiefly in its larger towns.

According to the U.S. Census Bureau, the county has a total area of 476 square miles (1,230 km²), of which 476 square miles (1,230 km²) is land and 0.2 square miles (0.52 km²) (0.04%) is water.

Unlike most of Tennessee, a sizable part of northern Robertson County is outside of the Sun Belt due to a past error surveying the northern border of Middle and East Tennessee. Downtown Springfield in particular is north of the Sun Belt. The Sun Belt is defined by the Kinder Institute as being south of 36°30'N latitude, which was intended to be the northern border of Tennessee and is the actual northern border of West Tennessee.

As of the 2020 United States census, there were 72,803 people, 26,577 households, and 20,378 families residing in the county.