Ballygallum () is a townland, south of Downpatrick in County Down, Northern Ireland. The townland is approximately in area. It is situated in the civil parish of Bright and the historic barony of Lecale Upper.
Ballygallum was recorded as Ballyogalme in 1549, Balliogalline in 1603, and Ballygallin alias Ballygallind in 1632. While the final element of the name might suggest a derivation from the Irish word gallán, meaning "standing stone" or "pillar stone", linguistic and historical evidence indicates that the name more likely originates from a surname. The most plausible interpretation is Baile àgColaim, meaning "townland of the OâÂÂColms". The surname àColaim is considered a variant of Mac Colaim (anglicised as MacCollum), which is described by Woulfe (1923, p. 335) as an Ulster surname predominantly found in the counties of Antrim, Tyrone, and Donegal.
Townlands that border Ballygallum include: