Gerard of Cremona (Latin: Gerardus Cremonensis; c. 1114 – 1187) was an Italian translator of scientific books from Arabic into Latin. He worked in Toledo, Kingdom of Castile and obtained the Arabic books in the libraries at Toledo. Some of the books had been originally written in Greek and, although well known in Byzantine Constantinople and Greece at the time, were unavailable in Greek or Latin in Western Europe. Gerard of Cremona is the most important translator among the Toledo School of Translators who invigorated Western medieval Europe in the twelfth century by transmitting the Arabs' and ancient Greeks' knowledge in astronomy, medicine and other sciences, by making the knowledge available in Latin. One of Gerard's most famous translations is of Ptolemy's Almagest from Arabic texts found in Toledo.

Confusingly, there appear to have been two translators of Arabic text into Latin known as Gerard of Cremona. The first was active in the 12th century and concentrated on astronomy and other scientific works, while the second was active in the 13th century and concentrated on medical works.

Gerard was born in Cremona in northern Italy. Dissatisfied with the philosophies of his Italian teachers, Gerard went to Toledo. There he learned Arabic, initially so that he could read Ptolemy's Almagest, which had a traditionally high reputation among scholars, but which, before his departure to Castile, was not yet known in Latin translation. The first Latin translation was made, from the Greek around 1160 in Sicily. Although we do not have detailed information of the date when Gerard went to Castile, it was no later than 1144.

Toledo, which had been a provincial capital in the Caliphate of Cordoba and remained a seat of learning, was safely available to a Catholic like Gerard, since it had been conquered from the Moors by Alfonso VI of Castile in 1085. Toledo remained a multicultural capital, insofar as its rulers protected the large Jewish and Muslim quarters, and kept their trophy city an important centre of Arab and Hebrew culture. One of the great scholars associated with Toledo was Rabbi Abraham ibn Ezra, Gerard's contemporary. Mozarabic culture was common in the area. The city was full of libraries and manuscripts, and was one of the few places in medieval Europe where a Christian could be exposed to Arabic language and culture.

In Toledo Gerard devoted the remainder of his life to making Latin translations from the Arabic scientific literature.

Gerard of Cremona's Latin translation of the Arabic version of Ptolemy's Almagest made c. 1175 was the most widely known in Western Europe before the Renaissance. Unbeknownst to Gerard, an earlier translation of the Almagest had already been made in Sicily from the original Greek c. 1160 under the aegis of Henricus Aristippus, although this version was not as widely used in the Middle Ages as Gerard's version. George of Trebizond and then Johannes Regiomontanus retranslated it from the Greek original in the fifteenth century. The Almagest formed the basis for Western astronomy until it was eclipsed by the theories of Copernicus.

Gerard edited for Latin readers the Tables of Toledo, the most accurate compilation of astronomical data ever seen in Europe at the time.^{[citation needed]} The Tables were partly the work of Al-Zarqali, known to the West as Arzachel, a mathematician and astronomer who flourished in Cordoba in the eleventh century.

Al-Farabi, the Islamic "second teacher" after Aristotle, wrote hundreds of treatises. His book on the sciences, Kitab lhsa al Ulum, discussed classification and fundamental principles of science in a unique and useful manner. Gerard rendered it as De scientiis (On the Sciences).