1090 (MXC) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar.
Events
By area
Africa
Béjaïa becomes the capital of the Hammadid Dynasty in Algeria.
Europe
Third expedition of the Almoravid army in al-Andalus who subdue the taifas kingdoms. Córdoba, Seville, Grenada, Málaga, Almería and Ronda fall to the troops of Yusuf ibn Tashfin.
By topic
Arts and culture
Troubadours begin playing in Provence.
Technology
Song Dynasty Chinese writer Qin Guan writes the Can Shu (Book of Sericulture), which describes a silk-reeling machine that has the world's oldest known mechanical belt drive.
Births
Saint Bernard of Clairvaux (d. 1153) Eliezer ben Nathan of Mainz Qin Hui, Chinese Song Dynasty Prime Minister (d. 1155)
Deaths
June 26 – Jaromír (Bishop of Prague) July 3 – Egbert II, Margrave of Meissen (b. c. 1060) October 6 – Saint Adalbero