Rieneck (German: [ˈʁiːnɛk] ⓘ) is a town in the Main-Spessart district in the Regierungsbezirk of Lower Franconia (Unterfranken) in Bavaria, Germany.

During the Middle Ages, the Counts of Rieneck were in competition with the Prince-Bishops of Würzburg and the Archbishops of Mainz for control of parts of the Spessart hills.

The Amt of the County of Rieneck, which the Counts of Nostitz had sold in 1803 to the Princes of Colloredo-Mansfeld, was mediatized in favour of the Principality of Aschaffenburg in 1806 and passed (by this time it had become a part of the Grand Duchy of Frankfurt) to Bavaria in 1814.

The greater part of Rieneck's workers commute to the nearby regional centres of Lohr am Main (Bosch Rexroth AG), Karlstadt and Würzburg.

The Sinn valley floodplain (Sinntalaue), which in the late 1990s became a nature reserve, provides a habitat for rare animals, like the beaver, and protected plants, like the snake's head.

Since 1959, it has housed a modern Jugendburg (a youth meeting and training centre) run by the Verband Christlicher Pfadfinderinnen und Pfadfinder, a Christian Guiding and Scouting organization.

The Romanesque Dreikonchenkapelle (chapel) is built into the 8 m-thick walls of the Dicker Turm ("Thick Tower") in a cloverleaf shape.

[1] The town's arms might be described thus: Quartered, first and fourth Or three chevrons gules, second and third barry of ten of the same, the whole surmounted at the fess point by a wheel spoked of six argent.

Just under 160 handicapped people (as of October 2007) live there with families who care for them, and they work in their own workshops, market gardens, dairies and bakeries.