|Ab urbe condita||1852|
|Balinese saka calendar||1020–1021|
|English Regnal year||12 Will. 2 – 13 Will. 2|
|Chinese calendar||戊寅年 (Earth Tiger)|
3795 or 3735
— to —
己卯年 (Earth Rabbit)
3796 or 3736
|- Vikram Samvat||1155–1156|
|- Shaka Samvat||1020–1021|
|- Kali Yuga||4199–4200|
|Japanese calendar||Jōtoku 3 / Kōwa 1|
|Minguo calendar||813 before ROC|
|Seleucid era||1410/1411 AG|
|Thai solar calendar||1641–1642|
1225 or 844 or 72
— to —
1226 or 845 or 73
|Wikimedia Commons has media related to 1099.|
- Siege of Jerusalem during the First Crusade:
- January 13 – Crusaders set fire to Mara, Syria.
- June 7 – The First Crusade: The Siege of Jerusalem begins.
- July 8 – 15,000 starving Christian soldiers march around Jerusalem.
- July 15 – Christian soldiers under Godfrey of Bouillon, Robert II of Flanders, Raymond IV of Toulouse and Tancred take Jerusalem at the end of this difficult siege.
- July 22 – The Kingdom of Jerusalem is founded in the Middle East.
- August 12 – Battle of Ascalon: The Crusaders defeat the Fatimids.
- Muhammad al-Idrisi, Sicilian Muslim cartographer, Egyptologist (d. 1165)
- Ranulf de Gernon, 4th Earl of Chester (d. 1153)
- William X, Duke of Aquitaine (d. 1137)
- Raymond of Poitiers, uncle of Eleanor of Aquitaine (d.1149) (approximate date)
- Approximate date – Henry of Blois, Norman bishop of Winchester (d. 1171)
- April 14 – Conrad, Bishop of Utrecht (b. before 1040)
- April 20 – Peter Bartholomew, French soldier, mystic (b. 1061)
- June 10 – El Cid, Castilian nobleman, military leader (b. 1043)
- July 29 – Pope Urban II (b. 1035)
- December 3 – Saint Osmund of Salisbury (b. 1065)