Montgomery County is a county located in the southern portion of the U.S. state of Georgia. As of the 2020 United States census, the population was 8,610. The county seat is Mount Vernon. Montgomery County is part of the Vidalia, GA micropolitan statistical area.

Montgomery County is named in honor of Richard Montgomery, an American Revolutionary War general killed in 1775 while attempting to capture Quebec City, Canada. It was created on December 19, 1793, from a southern portion of Washington County, Georgia.

Arthur Lott's Plantation was designated the first county seat in 1797.

In 1801, Tattnall County, Georgia was formed from the southern part of Montgomery County. The dividing line between Tatnall and Montgomery ran from the mouth of Limestone Creek on the Oconee River, just below modern Mount Vernon, Georgia, to the mouth of Wolf Creek on the Canoochee River below Metter, Georgia.

On December 11, 1811, the county lines between Washington County, Montgomery County, and Laurens County were adjusted by the Georgia General Assembly. The northern section of Montgomery between the Oconee River and the Ohoopee River was transferred to Laurens. On December 10, 1812, the county line of Montgomery was significantly adjusted as part of the creation of Emanuel County. Its new boundaries became from the then Laurens and Telfair county line on the Oconee River to the north prong of the Little Ocmulgee River (near present Chauncey, Dodge County, Georgia) down the Little Ocmulgee River as it meanders to its confluence with the Ocmulgee River then downstream as it meanders to the Oconee River, then North 30 degrees to Milligan's Creek in Tatnall County, and then with it to the Montgomery County line. Pendleton Creek (in modern Treutlen and Toombs counties) was used as the border between Montgomery and Emanuel. Because of these transitions Montgomery regained part of the land it had lost in the creation of Tatnall County in 1801 (land along the lower Oconee River), but also lost land along the upper Oconee River to Laurens County.

The creation of Emanuel County put the old county seat within Emanuel's border. On December 12, the Georgia General Assembly appointed the justices of the inferior court of Montgomery county to a commission to designate a new county seat and called for county business to be held until then at the home of James Alston. In 1813, the General Assembly recognized Mount Vernon as the new county seat.

The county line between Telfair County and Montgomery was adjusted once again in 1820 by the Georgia Genera Assembly. The new line differed in the upstream portion of the Little Ocmulgee River and better defined the line and gave Montgomery a small border with Pulaski County, Georgia and Telfair County some land on the northeast side of the Little Ocmulgee River. The line was to go upstream to its fork then to Browning's mill, a straight line to the mouth of Joiner's Creek (Near modern McRae, Georgia) at the second fork of the Little Ocmulgee River, and then up the second prong to Pulaski County Line.

The land gained by Telfair County from Montgomery County on the northeast side of the Little Ocmulgee River was reversed by the Georgia General Assembly on December 18, 1833.