Sleaford Mere is a permanent saline lake, located on the Jussieu Peninsula on the south eastern tip of Eyre Peninsula in South Australia about 15km south west of Port Lincoln. The lake was discovered and named by Matthew Flinders on 26 February 1802. Since 1969, the lake has been part of the Sleaford Mere Conservation Park and since 2005, it has been listed as a nationally important wetland. The lake and its environs are notable as a venue for recreational pursuits such as canoeing.