Guillaume Courtet (1589-1637) was a French Dominican priest who has been described as the first Frenchman to have visited Japan. He was martyred in 1637 and canonized in 1987.
In 1636, Guillaume Courtet penetrated Japan clandestinely, with the objective of furthering Western efforts to promote Christianity there. He was accompanied by a Spanish friend named Miguel de Ozaraza.
Entering Japan was a very dangerous endeavour, as Christianity had been prohibited in the country since 1613. Courtet entered the country under the Spanish name Tomaso de Santo Domingo. He sailed from the Philippines and disembarked in Ishigaki-jima, but a few days later he was caught and imprisoned for one year. From there he was brought to Kagoshima and then Nagasaki.
In an attempt to make him apostacize, he was tortured by submission to the "torture of the water", the "torture of the alênes" (needles under the fingernails) and the hanging torture of tsurushi. He remained true to his faith, however, and as a result he was beheaded with his friends on September 29, 1637.
Guillaume Courtet became a saint on October 18, 1987.