Eystein I (cirka 1088–1123) (Norwegian: Øystein) was king of Norway 1103-1123.

Eystein became king together with his brothers Sigurd and Olav when his father Magnus Barefoot died in 1103.

Whereas Sigurd made Norway known abroad, Eystein worked for economic and cultural progress in Norway constructing several churches, Munkeliv monastery in Bergen, a port in Agdenes and hostels for travellers. His relationship to Sigurd was strained, but open conflict was avoided.