Mühledorf was a municipality in the Bucheggberg district in the canton of Solothurn, Switzerland. On 1 January 2014, the former municipalities of Mühledorf, Aetingen, Aetigkofen, Bibern, Brügglen, Gossliwil, Hessigkofen, Küttigkofen, Kyburg-Buchegg and Tscheppach merged into the new municipality of Buchegg.