Christoforo Borri (1583 in Milan – 24 May 1632 in Rome), also called Christopher Borrus in older English sources, was a Jesuit missionary in Vietnam, a mathematician, and an astronomer.
He became a member of the Society of Jesus, 16 September 1601; in 1616 he was sent from Macau with the Jesuit priest Marquez, as one of the first missionaries to Đàng Trong (knowns to the Europeans as Cocincina, now part of central Vietnam).
The work was considered one of the best sources of information concerning Cochinchina on account of its detailed description of the physical, political, and ecclesiastical conditions of the country.
According to Kircher (1641) he drew up the first chart for the Atlantic and Indian Oceans showing the spots where the magnetic needle makes the same angles with the meridian; if this is true, he should be regarded as the forerunner of Edmund Halley.
In another manuscript, now in Évora, Tratado da arte de navegar pelo Cristovao Bruno, which bears on the same subject, he makes suggestions, according to Allatius (1633), as to a new method for determining the longitude at sea and also concerning improvements in sea-charts.