Mjölby (Swedish pronunciation: [ˈmjø̌ːlbʏ] ⓘ or [ˈmjœ̌lːbʏ]) is a city and the seat of Mjölby Municipality, Östergötland County, Sweden with 28,544 inhabitants in 2024.

The name Mjölby is derived from Mölloby, which comes from mylna or mölna, meaning 'mill'.

Due to the rapids of Svartån and the fertile soils of the surrounding plains, Mjölby is a natural place for a mill.

During the Dacke War in 1542–1543, Mjölby was the northernmost point reached by the rebels from Småland.

This article about a location in Östergötland County, Sweden is a stub.