The Mästermyr chest is a Viking Age (793–1066) tool chest found in the Mästermyr mire west of Hemse on the island of Gotland, Sweden. It is the largest tool find from that era in Europe.
During the Viking Age, the area where Mästermyr mire is located used to be a lake. The mire was drained in 1902–10. In October 1936, the chest was found by farmer Hugo Kraft in a field owned by Emil Norrby in Snoder, Sproge near Hemse. It was found in an area that was plowed for the first time.
The chest is on display in the Swedish History Museum in Stockholm.
Most of the find had been placed in the chest, but there were also objects around it such as three bronze cauldrons, three bells and a fire-grid of iron. A chain, made up of 26 figure-of-eight shaped links, was wrapped around it. It served both as an extra lock and handle since the chest was too heavy for the original handle. The chest and the other items had probably been placed in a boat which capsized and sank in the lake. Another theory is that the chest was temporarily hidden at the water's edge.
The chest contained Viking-era blacksmithing and woodworking tools. It also contained several products of such work, including elements of several locks. The chest and its contents provide a valuable insight into technology during the Viking Age.
The chest, 90 cm (35 in) long, 26 cm (10 in) wide and 24 cm (9.4 in) high, was made of oak with iron hinges and lock. It was intact despite the rough encounter with the plow. It was rectangular with a slightly curved lid and flat bottom. The bottom was joined to the ends via a mortise and through tenon. Pegs were used to attach the sides to the bottom and end pieces. The ends and sides were trapezoidal and slightly angled. A lock wrought from iron was attached to the front side of the chest.
Given the wide range of tools and objects in varying styles in the find, and the lack of coins or other chronological markers, it has been impossible to determine an exact date for the chest. The wider term "Viking Age" around 1000, is used for dating it.