Travis County has had two locations named Montopolis. The first was during the Republic of Texas period north of the Colorado River. The second is today's Montopolis neighborhood in Austin, Texas south of the river. Located southeast of the city's urban core, today's neighborhood is in ZIP code 78741. Montopolis is bounded by Lady Bird Lake on the north, by Grove Street and the Pleasant Valley neighborhood on the west, to the south by Texas State Highway 71, and by U.S. Route 183 on the east. The southeast corner abuts Austin-Bergstrom International Airport. Montopolis is in City Council District 3.

Travis County has had two locations named Montopolis that differ in their formation and location, sometimes causing confusion when the two are conflated.

The first was a planned townsite by Jesse Cornelius Tannehill during the Republic of Texas period north of the Colorado River, east and adjacent to what would become Austin, with a systematic design of building lots, farm lots, out lots, and streets laid out on a grid much like Edwin Waller's design of Austin.

The second was a community south of the Colorado River that began taking shape in Texas' Reconstruction era and into the early 20th century, evolving over several decades and ultimately becoming the neighborhood most Austinites recognize today as Montopolis.

The common thread joining old and new Montopolis is a historic river crossing become ferry then bridge of the same name with history that predates both.

The founder of the Republic of Texas era townsite of Montopolis was Jesse Cornelius Tannehill (1797-1863). A recent though often repeated misconception is that Tannehill's Montopolis was founded in 1830; Tannehill's time in Texas is well documented showing this is not so. Tannehill and family came to Texas in 1828 first settling near Caney in Matagorda County. As a member of Stephen F. Austin's "Little Colony", they soon moved to Bastrop. In 1836 during the Texas war for independence, when Mexican forces threatened settlements along the Colorado, the Tannehills and other families fled Bastrop in wagons eastward towards Nacogdoches along the Old San Antonio Road. This evacuation was referred to as the Runaway Scrape. Following the war, the Tannehills lived in Huntsville and later in La Grange until 1839.

In 1839, Tannehill, his wife, Jane L. (Richardson) Tannehill (1803-1855), their children, and possibly several enslaved persons, moved to a headright of 4,428 acres on the Colorado River, from which 800 acres were surveyed for the town tract. A partnership deed between Tannehill and five others recorded July 2, 1839, established the location of a platted town on the left (north) bank of the Colorado river. Tannehill never owned any part of the Santiago del Valle grant south of the Colorado, nor was he in any way responsible for development or settlement south of the Colorado River, where the current community of Montopolis is located.

The townsite was named Montopolis ("mont" Latin for "mountain" and "polis" Greek for "city"). A recent interpretation of Montopolis is "city on a hill". In research for the Montopolis historical marker no primary or contemporary evidence for this was found. Several families settled in the community. James Smith (1790-1845) was likely the first settler in 1838. His 1841 home is preserved on Boggy Creek Farm.