Baby of the House is the unofficial title given to the youngest member of a parliamentary house. The term is most often applied to members of the British parliament from which the term originated. The title is named after the Father of the House, which is given to the longest serving member of the British and other parliaments.

Father of the House is a title that has been traditionally bestowed, unofficially, on certain members of some legislatures, most notably the House of Commons in the United Kingdom. In some legislatures the title refers to the longest continuously serving member, while in others it refers to the oldest member. Recently, the title Mother of the House or Mother of Parliament has also been used, although the usage varies among countries; it is either the female alternative to Father of the House, being applied when the relevant member is a woman, or refers to the oldest or longest-serving woman without reference to male members.