In genealogy, a top ancestor is the oldest ancestor in a continuous sequence of ancestors. This means that a continuous line of parent-child connections exists between the top ancestor and the subject of the genealogical study, such as a living person. However, the top ancestor's parents are not (or not yet) known.
Top ancestors are sometimes used to describe the status of a genealogical research project, or in order to compare the availability of genealogical data in different times and places. Often, top ancestors are implied to be patrilineal. If a patrilineal dynasty is considered, each such dynasty has exactly one top ancestor.