An engagement, betrothal, or fiancer is a promise to wed, and also the period of time between a marriage proposal and a marriage. During this period, a couple is said to be betrothed, intended, affianced, engaged to be married, or simply engaged. Future brides and grooms may be called the betrothed, a wife-to-be or husband-to-be, fiancée or fiancé (from the French word of the same form), respectively. The duration of the courtship varies vastly, and is largely dependent on cultural norms or upon the agreement of the parties involved.

Long engagements were once common in formal arranged marriages, and it was not uncommon for parents betrothing children to arrange marriages many years before the engaged couple were old enough. This is still common in some countries.