The Constitution of the Commonwealth of Massachusetts is the fundamental governing document of the Commonwealth of Massachusetts. It was written by John Adams, Samuel Adams, and James Bowdoin. The constitution was adopted in 1780 and is the oldest functioning written constitution in continuous effect in the world.

The Massachusetts Constitution was the last of the first set of the state constitutions to be written. Consequently, it was more sophisticated than many of the other documents. Among the improvements was the structure of the document itself: instead of just a listing of provisions, it had a structure of chapters, sections, and articles. This structure was replicated by the US Constitution. It also had substantial influence on the subsequent revisions of many of the other state constitutions. The Massachusetts Constitution has four parts: a preamble, a declaration of rights, a description of the framework of government, and articles of amendment.