Martino Martini (20 September 1614 – 6 June 1661) was a Jesuit missionary in China. Born and raised in Trento, he worked as a cartographer and historian of ancient imperial China.

Martini was born in Trento, in the Bishopric of Trent, Holy Roman Empire. After finishing high school in Trento in 1631, he joined the Society of Jesus, continuing his studies of classical literature and philosophy at the Roman College in Rome (1634–1637). However, his main interest was astronomy and mathematics, which he studied under the supervision of Athanasius Kircher. His request to undertake missionary work in China was eventually approved by Mutius Vitelleschi, the then Superior General of the Jesuits. He pursued his theological studies in Portugal (1637–1639), where he was ordained priest (1639, in Lisbon).

He set out for China in 1640 and arrived in Portuguese Macau in 1642, where he studied Chinese for some time. In 1643 he crossed the border and settled in Hangzhou, Zhejiang Province, from where he did much travelling in order to gather scientific information, especially on the geography of the Chinese empire: he visited several provinces, as well as Peking and the Great Wall. He made great use of his talents as missionary, scholar, writer and superior.

Soon after Martini's arrival in China, the Ming capital, Beijing, fell to Li Zicheng's rebels (April 1644) and then to the Qing dynasty, and the last legitimate Ming emperor, the Chongzhen Emperor, hanged himself. Down in Zhenjiang, Martini continued working with the short-lived regime of Zhu Yujian, Prince of Tang, who set himself up as the (Southern) Ming Longwu Emperor. Soon enough, the Qing troops reached Zhejiang. According to Martini's report (which appeared in some editions of his De bello tartarico), the Jesuit was able to switch his allegiance to China's new masters in an easy but bold way. When Wenzhou, in southern Zhejiang, where Martini happened to be on a mission for Zhu Yujian, was besieged by the Qing and was about to fall, the Jesuit decorated the house where he was staying with a large red poster with seven characters saying, "Here lives a doctor of the divine Law who has come from the Great West". Under the poster, he set up tables with European books, astronomical instruments, etc., surrounding an altar with an image of Jesus. When the Qing troops arrived, their commander was sufficiently impressed with the display to approach Martini politely and ask if he wished to switch his loyalty to the new Qing Dynasty. Martini agreed and had his head shaved in the Manchu way, and his Chinese dress and hat were replaced with Qing-style ones. The Qing then allowed him to return to his Hangzhou church and provided him and the Hangzhou Christian community with the necessary protection.

In 1651, Martini left China for Rome as the Delegate of the Chinese Mission Superior. He took advantage of the long, adventurous voyage (going first to the Philippines, from thence on a Dutch privateer to Bergen, Norway, which he reached on 31 August 1653, and then to Amsterdam). Further, and still on his way to Rome, he met printers in Antwerp, Vienna and Munich to submit to them historical and cartographic data he had prepared. The works were printed and made him famous.

When passing through Leyden, Martini was met by Jacobus Golius, a scholar of Arabic and Persian at the university there. Golius did not know Chinese, but had read about "Cathay" in Persian books, and wanted to verify the truth of the earlier reports of Jesuits such as Matteo Ricci and Bento de Góis who believed that Cathay was the same place as China, where they lived or visited. Golius was familiar with the discussion of the "Cathayan" calendar in Zij-i Ilkhani, a work by the Persian astronomer Nasir al-Din al-Tusi, completed in 1272. When Golius met Martini (who, of course, knew no Persian), the two scholars found that the names of the 12 divisions into which, according to Nasir al-Din, the "Cathayans" were dividing the day, as well as those of the 24 sections of the year reported by Nasir al-Din matched those that Martini had learned in China. The story, soon published by Martini in the "Additamentum" to his Atlas of China, seemed to have finally convinced most European scholars that China and Cathay were the same.

On his way to Rome, Martini met his then 10-year-old cousin Eusebio Kino, who later became another famed Jesuit missionary explorer and the world-renowned cartographer of New Spain.

In the spring of 1655, Martini reached Rome. There, in Rome, was the most difficult part of his journey. He had brought along (for the Holy Office of the Church) a long and detailed communication from the Jesuit missionaries in China, in defence of their inculturated missionary and religious approach: the so-called Chinese Rites (Veneration of ancestors, and other practices allowed to new Christians). Discussions and debates took place for five months, at the end of which the Propaganda Fide issued a decree in favour of the Jesuits (23 March 1656). A battle was won, but the controversy did not abate.