Who is the Steward of Gondor during the War of the Ring?

The Steward of Gondor during the War of the Ring is Denethor. More precisely, Denethor II is the 26th ruling Steward of Gondor, governing from Minas Tirith while the throne remains vacant.

Denethor is the son of Ecthelion II and the father of Boromir and Faramir. He is a powerful, intelligent, and proud ruler, but grief and fear gradually overwhelm his judgment. His wife, Finduilas, dies young, and Boromir's death deepens his despair.

During the war, Denethor secretly uses the palantír of Minas Tirith to observe Sauron's strength. Because Sauron controls what he sees, Denethor becomes convinced that Gondor is doomed. He still directs the city's defence, orders the beacons lit, and summons aid, but his leadership collapses after Faramir is gravely wounded.

A common mix-up is confusing Denethor with Faramir, who becomes Steward only after Denethor's death. Aragorn ultimately restores the royal line and becomes King Elessar, ending the long period in which Gondor was ruled by Stewards.