Pete Seeger, the singer, folk-song collector and songwriter who spearheaded an American folk revival and spent a long career championing folk music as both a vital heritage and a catalyst for social change, died Monday. He was 94 and lived in Beacon, N.Y.

His death was confirmed by his grandson, Kitama Cahill Jackson, who said he died of natural causes at NewYork-Presbyterian Hospital.

Mr. Seeger’s career carried him from singing at labor rallies to the Top 10 to college auditoriums to folk festivals, and from a conviction for contempt of Congress (after defying the House Un-American Activities Committee in the 1950s) to performing on the steps of the Lincoln Memorial at an inaugural concert for Barack Obama.

For Mr. Seeger, folk music and a sense of community were inseparable, and where he saw a community, he saw the possibility of political action.

In his hearty tenor, Mr. Seeger, a beanpole of a man who most often played 12-string guitar or five-string banjo, sang topical songs and children’s songs, humorous tunes and earnest anthems, always encouraging listeners to join in. His agenda paralleled the concerns of the American left: He sang for the labor movement in the 1940s and 1950s, for civil rights marches and anti-Vietnam War rallies in the 1960s, and for environmental and antiwar causes in the 1970s and beyond. “We Shall Overcome,” which Mr. Seeger adapted from old spirituals, became a civil rights anthem.

Mr. Seeger was a prime mover in the folk revival that transformed popular music in the 1950s. As a member of the Weavers, he sang hits including Lead Belly’s “Goodnight, Irene” — which reached No. 1 — and “If I Had a Hammer,” which he wrote with the group’s Lee Hays. Another of Mr. Seeger’s songs, “Where Have All the Flowers Gone?,” became an antiwar standard. And in 1965, the Byrds had a No. 1 hit with a folk-rock version of “Turn! Turn! Turn!,” Mr. Seeger’s setting of a passage from the Book of Ecclesiastes.

Mr. Seeger was a mentor to younger folk and topical singers in the ‘50s and ‘60s, among them Bob Dylan, Don McLean and Bernice Johnson Reagon, who founded Sweet Honey in the Rock. Decades later, Bruce Springsteen drew the songs on his 2006 album, “We Shall Overcome: The Seeger Sessions,” from Mr. Seeger’s repertoire of traditional music about a turbulent American experience, and in 2009 he performed Woody Guthrie’s “This Land Is Your Land” with Mr. Seeger at the Obama inaugural. At a Madison Square Garden concert celebrating Mr. Seeger’s 90th birthday, Mr. Springsteen introduced him as “a living archive of America’s music and conscience, a testament of the power of song and culture to nudge history along.”