When were European firearms first introduced to the Korean Peninsula?

The first European firearm ever made in Korea was breech-loading swivel gun, which was introduced from Ming Dynasty China (who in turn acquired them from the Portuguese around 1517) some time around mid 16th century. The inscription on the oldest swivel gun excavated in Korea states that it was casted in 1563.

Arquebus was the next, introduced to Korea by Chinese engineers and surrendered Japanese soldiers during the Japanese invasions of Korea (1592–1598). Records from the 《Veritable Records of the Joseon Dynasty》 suggest that the first prototypes were made sometime around March 1593 under the tutorage of a Chinese smith.