Österlånggatan (Swedish: Eastern Long Street) is a street in Gamla stan, the old town of , Sweden. Stretching southward from Slottsbacken to , it forms a parallel street to Baggensgatan and Skeppsbron. Major sights include the statue of Saint George and the Dragon on Köpmanbrinken and the restaurant Den Gyldene Freden on number 51, established in 1722 and mentioned in Guinness Book of Records as one of the oldest with an unaltered interior.
Like Västerlånggatan, Österlånggatan used to pass outside of the city walls and was for many centuries one of the city's major streets. (See Västerlånggatan for more details.) When Skeppsbron, the broad street and quay running to the east of Österlånggatan, was created during the 17th century, Österlånggatan lost much of the importance it used to have. Compared to Västerlånggatan, Österlånggatan is today a relatively quiet street notwithstanding the many restaurants and shops, in sharp contrast to the neighbourhood when the street formed the backyard of the dock district, crowded with sailors, taverns, travellers, and traders.
During the 13th century, Österlånggatan was little more than the eastern shoreline, and archaeological excavations have unveiled the original beaten track some three metres below today's pavement. The shore line was, however, gradually pushed eastward by land fillings of gravel and rubbish. In the 14th century, the street had become the 'long street east of the wall' (e.g. Österlånggatan), far from the water, paved and lined-up with workshops, shops, and dwellings. German merchants lived in and around , while Swedish merchant's from Bergslagen, the mining district north of the capital, resided on Österlånggatan, and only a few of the noble families settled here during the Middle Ages. One of them was Gunilla Johansdotter Bese (1473–1553), who lived in the now closed alley still carrying her name, Fru Gunillas Gränd, between Numbers 43 and 45.