Ruling Stewards was the title used for the Stewards of Gondor who came into power after EƤrnur, the last of the Kings of Gondor, was lost.

The first of the Ruling Stewards was Mardil and the last was Denethor who perished by his own hand during the War of the Ring. His son, Faramir, would have become the next Ruling Steward had Aragorn not returned to claim his rightful place as the King of both Arnor and Gondor.
Encyclopedia entry originally written by Nienna-of-the-Valar