Jointure was a legal concept used largely in late mediaeval and early modern Britain, denoting the estate given to a married couple by the husband's family. One of its most important functions was providing a livelihood for the wife if she became widowed, and it is most often used in this sense, interchangeably with dower.

In practice

After marriage, the father of the husband would settle lands or income on the couple to enable them to lead an economically independent life. This usually took the form of a settlement by deed, giving the couple joint tenancy for the duration of their lives (ensuring that the wife would keep all of the property upon being widowed). In this case, the couple's jointure would form part or whole of the wife's promised dower. It is in this sense that the word is most often used.

The 1536 Statute of Uses introduced the concept of legal jointures into English law. The requirements for legal jointure were (1) that it 'must take effect immediately' when the husband died, (2) that it must be for the wife's lifetime or be terminable by her, (3) that it must be made before marriage takes place (if it was made after, the wife could choose to void it after being widowed), and (4) that it must represent the entirety of the dower owed to the widow. If the bride accepted any provision instead of a dower before marriage, she could not lay claim to one later; if she accepted a similar provision after marriage, she could choose between receiving a jointure or a dower (even if she had explicitly stated that she accepted the provision in place of a dower).

Following the introduction of legal jointures, jointures settled by a deed of joint tenancy were known as equitable jointures in law.