Ascelin of Lombardy, also known as Nicolas Ascelin or Ascelin of Cremona, was a 13th-century Dominican friar whom Pope Innocent IV sent as an envoy to the Mongols in March 1245. Ascelin met with the Mongol ruler Baiju, and then returned to Europe with a message and Mongol envoys in 1248.

Baiju (died 1260) was a general of the Mongol Empire and the Ilkhanate. He was the general responsible for the conquest of Anatolia in 1243 after the victory in the Battle of Sivas (Kose Dag), and led the advance from Syria to Egypt in 1259. Hulegu Khan had Baiju executed when the Mongol corps fled from the Mamelukes after the Battle of Ain Jalut.