Elmo's World is a segment that is shown at the end of the American children's television program Sesame Street which premiered on November 16, 1998, as part of a broader structural change to the show. It originally lasted fifteen minutes at the end of each episode. The segment ran until 2009, and then returned in 2017. The segment was designed to appeal to younger viewers and to increase ratings, which had fallen in the past decade. The segment is presented from the perspective of a three-year-old child as represented by its host, the Muppet Elmo, performed by Kevin Clash in the original series and Ryan Dillon in the 2017 reboot.

The segment was developed out of a series of workshops that studied changes in the viewing habits of Sesame Street's audience, and the reasons for the show's lower ratings. Elmo's World used traditional production elements, but had a more sustained narrative. In 2002, Sesame Street's producers changed the rest of the show to reflect its younger demographic and the increase in their viewers' sophistication.

Long-time writer Judy Freudberg came up with the concept of Elmo's World, and writer Tony Geiss and executive producer Arlene Sherman helped develop it. In contrast with the realism of the rest of the show, the segment presented Elmo moving between and combining a live action world and a computer-generated animated world, which looked like "a child's squiggly crayon drawing come to life", with "a stream-of-consciousness feel to it". Elmo's pet goldfish Dorothy and the members of the Noodle family were silent to allow Elmo to do all the talking, and to give children the opportunity to respond to what they saw on the screen. A brief clip from Elmo's World appears in Sesame Street's 2002–2006 intro.

In 2009, Elmo's World temporarily ceased production. It was replaced by Elmo: The Musical in 2012, and returned in 2017. The show is alternated by another Elmo-centered segment, Elmo & Tango’s Mysterious Mysteries, which was produced entirely with animation, in Sesame Street's 52nd season in 2021.