The Government of Ireland Act, which received Royal Assent on 23 December 1920, represented a pivotal shift in the constitutional landscape of the British Isles during the interwar period. By establishing the legal framework for the partition of Ireland, the legislation sought to resolve the long-standing and volatile question of Irish governance by creating two separate devolved parliaments: one for Northern Ireland and one for Southern Ireland. This act was intended to replace the suspended Home Rule Act of 1914, reflecting the British government's attempt to manage the escalating political tensions and the rise of republican sentiment across the island.

The implementation of the act fundamentally altered the relationship between Britain and Ireland, effectively formalising the division of the country into two distinct political entities. While the parliament for Northern Ireland was successfully established in Belfast, the provisions for Southern Ireland were never fully realised due to the ongoing Irish War of Independence and the subsequent negotiations that led to the Anglo-Irish Treaty of 1921. Consequently, the act remains a significant historical marker of the transition from the United Kingdom of Great Britain and Ireland towards the eventual creation of the Irish Free State.

• It established the legal basis for the partition of Ireland into two separate jurisdictions.
• It provided for the creation of devolved parliaments in both Northern Ireland and Southern Ireland.
• It served as a replacement for the earlier, unimplemented Home Rule Act of 1914.
• It marked a major transformation in the constitutional ties between Britain and Ireland.
• It was enacted during a period of intense political conflict and social upheaval.