Odorheiu Secuiesc is the second-largest city in Harghita County, Romania. In its short form, it is also known as Odorhei in Romanian and Udvarhely in Hungarian.
The town, as the former seat of the Udvarhely comitatus, is one of the historical centres of the Székely Land. The first known reference to the city was in a papal register of duties in 1333. Udvarhely was the location of the first national assembly of Székelys in 1357.
A fortress was built in the town in 1451. It was rebuilt and strengthened by John II Sigismund Zápolya in 1565, in order to control the Székelys. The latter, allied to the Wallachian Prince (and Habsburg partner) Michael the Brave during his campaign in Transylvania, destroyed the fortress in 1599. It was repeatedly rebuilt and destroyed again during history. The ruins of the structure are nowadays known as "The Székely-attacked fortress".
Odorheiu Secuiesc and the surrounding villages were hit by significant flooding in August 2005.
A statue park of historical persons important for the Székelys was unveiled in Odorheiu Secuiesc on May 22, 2004. This has created controversy, as one of the sculptures (The Wandering Szekler) was interpreted in the Romanian press as being that of writer, poet and convicted war criminal Albert Wass.