A townland or bally (Irish: Baile Fearainn) is a small geographical division of land used in Ireland. The townland system is of Gaelic origin, pre-dating the Normans, with most townlands believed to pre-date the Norman invasion and many retaining their Gaelic names. Some townland names and boundaries however derive from Norman manors, plantation divisions, or later creations of the Ordnance Survey. There are currently 61,402 named townlands in Ireland, covering the whole island.

In Ireland, a townland is the smallest administrative division of land. Whilst the concept of townlands is based on the Gaelic system of land division, it was in the 1600s that they became mapped and defined by the English administration for the purpose of portioning the land for investors or grants. The first official evidence of the existence of this Gaelic land division system can be found in church records from before the 12th century.

The term "townland" in English is derived from the Old English word tun, similar to the Irish word tuath, denoting an enclosure. The term describes the smallest units of land division in Ireland. These are based upon various different kinds of Gaelic land division, many of which had their own names.