South Down is an electoral constituency for the Northern Ireland Assembly. The seat was first used for a Northern Ireland-only election for the Northern Ireland Assembly in 1973. It usually shares boundaries with the South Down UK Parliament constituency, however the boundaries of the two constituencies were slightly different from 1983 to 1986 as the Assembly boundaries had not caught up with Parliamentary boundary changes and from 1996 to 1997 when members of the Northern Ireland Forum had been elected from the newly drawn Parliamentary constituencies but the 51st Parliament of the United Kingdom, elected in 1992 under the 1983–95 constituency boundaries, was still in session.