Year 942 (CMXLII) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar.
- Summer – The Hungarians invade Al-Andalus (modern Spain) and besiege the fortress city of Lerida. They devastate Cerdanya and Huesca, and capture Yahya ibn Muhammad ibn al Tawil, Umayyad governor (wali) of the town of Barbastro. Lacking food stores and sufficient forage, the Hungarians retreat to the Gothic March.
- Battle of Fraxinet: King Hugh of Provence launches an attack on Fraxinet, the Moorish fortress on the Côté d'Azur that had taken control of the Piedmontese valleys. With the assistance of a Byzantine fleet sent by Emperor Romanos I, Hugh lays siege to the Moorish fortress with the help of Hungarian auxiliary troops (Kabars).
- Fall – Hugh of Provence makes a truce with the Moors of Fraxinet, after hearing the news that a Swabian army is about to descend on Italy. He allows the Moors to attack the Alpine passes for his own political ends in his struggle with Berengar of Ivrea. The Byzantines cry foul and end their alliance with Hugh.
- December 17 – William I ("Longsword"), duke of Normandy, is ambushed and assassinated by supporters of Arnulf I ("the Great"), count of Flanders, while the two are at a peace conference at Picquigny (on an island on the Somme) to settle their differences. William is succeeded by his 9-year-old son Richard.
- Winter – The Hungarians raid Friuli and descend into central Italy. Hugh of Provence grants them a large sum of tribute if they return to the Gothic March or Spain. The Hungarians refuse the offer and raid the countryside of Lazio, destroying the region of Sabina.