Monica Barnes (née MacDermott; born 12 February 1936) is a former Irish Fine Gael politician. She was a Teachta Dála (TD) for the Dún Laoghaire constituency.
Educated at the Louis Convent, Carrickmacross, Co. Monaghan, Barnes unsuccessfully contested the 1981 general election in the Dún Laoghaire constituency, and after a further defeat at the February 1982 general election she was elected to the 16th Seanad on the Labour Panel.
She was first elected to Dáil Éireann at the November 1982 general election and retained her seat until losing it at the 1992 general election. She was re-elected at the 1997 general election and retired at the 2002 general election.
Barnes also unsuccessfully contested the European Parliament election for the Leinster constituency in 1979 and 1994.