Helgeandsholmen (Swedish: [ˈhêːlɡɛandsˌhɔlːmɛn]) is a small island in central Stockholm, Sweden. It is located north of Stadsholmen, and east of Strömsborg, with which, together with Riddarholmen, it forms Gamla stan, the old town of Stockholm. Helgeandsholmen contains the Riksdag Building and the Museum of Medieval Stockholm, and is connected to neighbouring islands through three bridges: Riksbron, Stallbron, and Norrbro. Despite the small size, it is very important as it contains the parliament building, the supreme decision-making body of the Kingdom of Sweden.

The terrace in the eastern end, called Strömparterren ("The Stream Parterr"), is a public park with a restaurant dating from 1832, while the flight of stairs leading down to the water is from 1807–1810. The quay west of the Riksdag Building once surrounded Sweden's central bank Sveriges Riksbank and was thus named Bankkajen ("The Bank Quay"), while the streets on southern and northern sides are called Norra/Södra Helgeandstrappan ("The Northern/Southern Helgeand Stairs"), all of them named in 1925.

First mentioned in a letter written in Latin July 28, 1320, the name Helgeandsholmen, a corruption of Helige andens holme ("Islet of the Holy Spirit"), appears as Latin: in insula dicta helghaanzsholm ("on the island called Helgeandsholm"). At the time, helgeandshus (Old Swedish: hälgha ands hus, hälandzhus, helghanzhhws, hälianshus) was a name used for charitable institutions spiritual in nature, in Stockholm first mentioned in a testament from April 24, 1301 (domus sancti spiritus).

Though one regular shaped island today, Helgeandsholmen was until quite recently a set of islets. Before the start of extensive archaeological excavations in 1978, it was traditionally believed that the present island once encompassed three islets:

As mentioned above, a charitable institution organized by a pious foundation was located on the island, receiving sick people, poor and elderly as well as foreigners, and accepting donations from burghers in city, through which the institution became an important landowner. The original Helgeandshuset ("The House of the Holy Spirit") probably dates back to the 13th century but is not mentioned until 1301. Rebuilt after a fire in 1410, it was moved to Riddarholmen by King Gustav Vasa (1496–1560) in 1531. Though the appearance of Helgeandshuset is not known, it is believed to have resembled similar institutions elsewhere and thus consist of a hospital ward and a church surrounded by other buildings and a graveyard.

Originally, Norrbro stretched diagonally across Helgeandsholmen from (what is today) Mynttorget to Gustav Adolfs torg. Though not mentioned until 1288, the first bridge is believed to have been built with the foundation of the city in 1252. Like virtually all bridges during the Middle Ages, Norrbro was built in wood, at the time considered appropriate as bridges then easily could be dismantled during sieges.

Drawbridges are mentioned in 1318, and the general urban code from the mid 14th century prescribes six cities around Lake Mälaren – Arboga, Enköping, Sigtuna, Strängnäs, Västerås and Uppsala – to share the costs of maintenance with Stockholm, thus indicating the bridge wasn't merely of interest to the city, but a vital part of the regional road system. These neighbouring cities gradually came to question this obligation however, and during the 16th and 17th centuries Stockholm was, bit by bit, to take charge of the bridge alone.

Until the 1640s, the width of the street varied from 10 to 20 ells (5.9–11.9 metres), but as the northern settlements were incorporated with the city in 1635, so was Helgeandsholmen, and the standard street width was regulated. Governor Klas Fleming (1592–1644) had Norrbro straightened out, in line with his own site on the street, and the width set to 24 ells (14.3 metres).