Heather Cassils is a Canadian-American artist and bodybuilder known for their interdisciplinary work that explores themes of gender, identity, and the body. Cassils was born in 1975 in Montreal, Canada, and is based in Los Angeles, California. Cassils' practice incorporates elements of performance art, photography, sculpture, and video to challenge societal norms and push the boundaries of the body as a medium. They often use their own body as a site of exploration and transformation, undergoing rigorous physical training and pushing themselves to the limits of endurance and strength.

One of Cassils' notable projects is "Cuts: A Traditional Sculpture," in which they collaborated with a film crew to document their process of building muscle mass through a strict bodybuilding regimen. The resulting video and photographic series challenge traditional notions of femininity and masculinity while raising questions about power, control, and vulnerability.

Cassils' work also explores issues related to transgender and non-binary identities, advocating for greater visibility and understanding. Their performance piece "Becoming an Image" involves a series of physical encounters with a 2,000-pound block of clay, symbolizing the transformation of the body and the shaping of identity. Cassils' work has been exhibited internationally at renowned institutions and events such as the Venice Biennale, the National Theatre in London, and the Museum of Contemporary Art in Los Angeles. They have received numerous awards and fellowships for their contributions to the arts, including a Guggenheim Fellowship in 2018.

Through their powerful and thought-provoking work, Heather Cassils challenges societal norms, explores the complexities of gender and identity, and invites viewers to critically engage with the body as a site of personal and cultural significance.