联合王国（英文：United Kingdom，缩写：UK，全名：大不列颠与北爱尔兰联合王国）的历史发展以英格兰王国为核心，逐次并入威尔斯公国、苏格兰王国和爱尔兰王国。目前联合王国的领土包含英格兰、威尔斯、苏格兰和北爱尔兰。

1535年，英格兰王国以《联合法案公章》合并威尔斯公国，再以《1707年联合法案》合并苏格兰王国成为大不列颠联合王国，再以《1800年联合法案》合并爱尔兰王国成为大不列颠与爱尔兰联合王国。1922年，爱尔兰自由邦脱离联合王国，但北爱尔兰留下。1927年，爱尔兰共和国成立，英国国名于是改为今日的名称（爱尔兰字样改为北爱尔兰）。

The history of the United Kingdom as a unified sovereign state began in 1707 with the political union of the kingdoms of England and Scotland, into a united kingdom called Great Britain. Of this new state the historian Simon Schama said "What began as a hostile merger would end in a full partnership in the most powerful going concern in the world... it was one of the most astonishing transformations in European history." A further Act of Union in 1800 added the Kingdom of Ireland to create the United Kingdom of Great Britain and Ireland.