A Geobukseon, also known as a turtle ship in western descriptions, was a type of large Korean warship that was used intermittently by the Royal Korean Navy during the Joseon dynasty from the early 15th century up until the 19th century. It was used alongside the panokseon warships in the fight against invading Japanese naval ships. The ship's name derives from its protective shell-like covering. One of a number of pre-industrial armored ships developed in Europe and in East Asia, this design has been described by some as the first armored ship in the world.

The first references to older, first-generation turtle ships, known as gwiseon (귀선;  Korean pronunciation:), come from 1413 and 1415 records in the Annals of the Joseon Dynasty, which mention a mock battle between a gwiseon and a Japanese warship. However, these early turtle ships soon fell out of use as Korea's naval preparedness decreased during a long period of relative peace. 

Turtle ships participated in the war against Japanese naval forces supporting Toyotomi Hideyoshi's attempts to conquer Korea from 1592 to 1598.  Korean Admiral Yi Sun-sin, who won all battles against the Japanese Navy, is credited with designing the improved turtle ship. From their first appearance in the Battle of Sacheon, his turtle ships, equipped with at least five different types of cannon, greatly contributed to winning 16 times in 16 battles against the Japanese Navy until they were destroyed, under the command of Won Gyun, in the Battle of Chilcheollyang. Their most distinguishable feature was a dragon-shaped head at the bow (front) that could launch cannon fire or flames from the mouth. Each was also equipped with a fully covered deck to protect against arrow fire, musket-shots, and incendiary weapons.  The deck was covered with iron spikes to discourage the enemy from attempting to board the ship.
Turtle ship
The Geobukseon is the most famous Korean warship, winning all 16 battles against the Japanese navy with which Toyotomi Hideyoshi attempted to conquer Korea from 1592 to 1598.