Össeby kyrkoruin, Medieval church ruin in Brottby, Sweden.

Össeby kyrkoruin is a roofless medieval church ruin in Brottby, Vallentuna Municipality, with stone walls and a floor where old gravestones are stored. The local heritage society added a bell tower, an altar and benches. A runestone from around 1100 stands by the church.

The church was built in the 13th century as a parish church and abandoned in 1837 due to deterioration. A lightning strike in 1856 caused further damage, and restoration work began in the 1970s.

Outside the ruin stands runestone Upplands runinskrifter 184, carved around 1100 and probably once set on a grave in the churchyard. Its inscription reads "Här ligger Huskarl" (Here lies Huskarl); a huskarl was a free retainer of a chieftain, though the word is also attested as a personal name in runic inscriptions. The stone is a detail to look for beside the walls.

The site is accessible year-round and provides 100 seating spaces from May to September for outdoor services and gatherings. The hilltop location offers good views of the surrounding landscape and is relatively easy to reach.

The runestone Upplands runinskrifter 184, standing by the ruin, dates from around 1100 and probably first stood on a grave in the churchyard. Its inscription reads "Here lies Huskarl"; huskarl meant a free servant of a chieftain but is also attested as a personal name in runic inscriptions.