Clement Greenberg was an influential American art critic known for his role in promoting the Abstract Expressionism movement during the mid-20th century. He championed artists like Jackson Pollock and Mark Rothko, emphasizing the importance of formal qualities in art, such as color and composition. Greenberg's essays and critiques helped shape the understanding of modern art, advocating for the idea that art should focus on its medium. His theories contributed to the development of Modernism and influenced many artists and critics, making him a key figure in the art world of his time.