Kai Nielsen is the name of:
Kai Nielsen (footballer) Kaj Nielsen (footballer) Kai Nielsen (sculptor) (1882–1924), Danish sculptor Kai Nielsen (philosopher) (1926–2021), American, Canada-based professor of philosophy Sixten Kai Nielsen (born 1978), Danish artist Kai Ewans, born Kai Nielsen, Danish jazz musician
See also Kay Nielsen (1886–1957), Danish illustrator, pronounced Kai