Mayo North and West was a parliamentary constituency represented in Dáil Éireann, the lower house of the Irish parliament or Oireachtas from 1921 to 1923.

The constituency elected 4 deputies (Teachtaí Dála, commonly known as TDs) to the Dáil, on the system of proportional representation by means of the single transferable vote (PR-STV).

Mayo North and West was created under the Government of Ireland Act 1920 as a 4-seat constituency, for the 1921 general election to the House of Commons of Southern Ireland, whose members formed the 2nd Dáil.

It covered the northern and western parts of County Mayo.

It succeeded the constituencies of North Mayo and East Mayo which were used to elect the members of the 1st Dáil and earlier UK House of Commons members.