Robert Hall Weir (/wɪər/ WEER; né Parber, born October 16, 1947) is an American musician and songwriter best known as a founding member of the Grateful Dead. After the group disbanded in 1995, Weir performed with The Other Ones, later known as The Dead, together with other former members of the Grateful Dead. Weir also founded and played in several other bands during and after his career with the Grateful Dead, including Kingfish, the Bob Weir Band, Bobby and the Midnites, Scaring the Children, RatDog, and Furthur, which he co-led with former Grateful Dead bassist Phil Lesh. In 2015, Weir, along with former Grateful Dead members Mickey Hart and Bill Kreutzmann, joined with Grammy-winning singer/guitarist John Mayer, bassist Oteil Burbridge, and keyboardist Jeff Chimenti to form the band Dead & Company. The band remains active.

During his career with the Grateful Dead, Weir played mostly rhythm guitar and sang many of the band’s rock & roll and country & western songs. In 1994, he was inducted into The Rock and Roll Hall of Fame as a member of the Grateful Dead.

Weir was born in San Francisco, California, to John (Jack) Parber (1929-2015), of Italian and German ancestry, and a fellow college student, Phyllis Inskeep (1924-1997), of German, Irish, and English ancestry, who later gave him up for adoption; he was raised by his adoptive parents, Frederic Utter and Eleanor Cramer Weir, in the suburb of Atherton.