Sezimovo Ústí is urbanistically fused with the neighbouring towns Tábor in the north and Planá nad Lužnicí in the south.

According to legend, Sezimovo Ústí was founded by Sezima, an illegitimate son of Witiko of Prčice.

The first mention of Ústí is from 1250, when the general chapter of the Dominican Order agreed to the consecration of the monastery church to Saint Dominic.

[3] In 1414, Jan Hus was invited to Sezimovo Ústí to preach in Kozí hrádek Castle, which led the radicalization of many people and establishment of Hussite movement.

[2] During World War II, Sezimovo Ústí was incorporated into Tábor, which lasted until 30 June 1945.

Kozí hrádek is a castle ruin near Sezimovo Ústí, known for activities of Jan Hus.

[11] The villa of Czechoslovak president Edvard Beneš in Sezimovo Ústí was his favourite place of recreation, and the site of his burial.

[2] Sezimovo Ústí is a part of the Commonwealth of towns with hussite past and tradition, along with other 11 Czech and 6 German municipalities.