Christopher Wolfgang John Alexander was an Austrian-born British-American architect and design theorist. He was an emeritus professor at the University of California, Berkeley. His theories about the nature of human-centered design have affected fields beyond architecture, including urban design, software, and sociology. Alexander designed and personally built over 100 buildings, both as an architect and a general contractor.

In software, Alexander is regarded as the father of the pattern language movement. The first wiki—the technology behind Wikipedia—led directly from Alexander's work, according to its creator, Ward Cunningham. Alexander's work has also influenced the development of agile software development.

In architecture, Alexander's work is used by a number of different contemporary architectural communities of practice, including the New Urbanist movement, to help people to reclaim control over their own built environment. However, Alexander was controversial among some mainstream architects and critics, in part because his work was often harshly critical of much of contemporary architectural theory and practice.