Uppland Runic Inscription 13, Viking runestone fragment at Husby burial ground in Ekerö, Sweden.

Uppland Runic Inscription 13 is a 65 cm high, 80 cm wide and 30 cm thick granite fragment with runes 10 cm high, crowning Björn Ironside's barrow, the largest mound in a Vendel-period burial field at Husby on Munsö. The rough grey stone, partly hidden by grass, shows faint carved lines but no readable runic characters; broken pieces lie beside it.

U 13 is a Viking Age granite fragment that crowns Björn Ironside's barrow, the largest mound in a Vendel-period burial field at Husby on Munsö. The field holds about 150 ancient monuments: 45 mounds, some 104 round stone settings and this runestone fragment. The barrow measures 20 m across and 5 m high, with a flattened top about 10 m wide.

The visible runes are about 10 cm high, and only a few can still be read: the name Torgöt and a phrase asking for his spirit and God's (mother). The fragment crowns Björn Ironside's barrow, the largest mound in a Vendel-period grave field at Husby on Munsö with about 150 ancient remains.

U 13 crowns Björn Ironside's barrow, the largest mound on a Vendel-period grave field at Husby on Munsö, about 540 by 35–140 m with some 150 ancient remains. The fragment, 65 cm high, 80 cm wide and 30 cm thick, lies on the flattened top, with broken pieces beside it. Approach from Husby gård, east of the ridge.

A drawing from the 1700s shows that this stone was already in place at that time. This makes it a notably continuous witness, with its position documented across more than three centuries.