St. Magnus Cathedral was founded in Kirkwall in 1137AD by Earl Rögnvald Kolsson of Norway, after he acquired the earldom of Orkney. Once completed, it was used to house the relics of St. Magnus, Rögnvald's uncle.

In 1158AD while construction was still under way, Rögnvald was killed by a Scottish chieftain. Following his death, his bones were eventually interred in the cathedral, and he was canonised in 1192AD.

St. Magnus Cathedral was built in a Norman style by English master masons possibly trained at Durham Cathedral. Local red and yellow sandstone was utilised, often laid in alternating courses, creating a striking polychromatic effect. At the time of completion, the church consisted of the choir, the crossing, the transepts, part of the nave, and an apse at the east end containing the shrine of St. Magnus.

Work in the late 12th and early 13th Century saw the choir extended to the east (along with the addition of the east window) and the nave extended westwards. Vaulting was also added throughout the cathedral.

The Protestant Reformation of 1560AD saw government forces suppressing a rebellion, besieging and destroying Kirkwall Castle. It was their intention to destroy St. Magnus Cathedral on the pretext that the rebels had hidden within its walls, but the intervention of Bishop Law prevented this.

in 1671AD, the spire was destroyed by lightning, and subsequently replaced by a squat pyramid roof. In the early 20th Century, this roof was removed, and replaced by a tall steeple, more in keeping with the original design.

Between 1154AD and 1468AD, Orkney fell under the ecclesiastical jurisdiction of a Norwegian archbishop. In 1468AD, Orkney was annexed by King James III of Scotland, and St. Magnus Cathedral and its bishopric came under the control of the Archbishop of St. Andrews. The bishopric continued to exist following the reformation, surviving until the Scottish revolution of 1688AD. A Scottish Episcopal Church bishopric encompassing Orkney was created in 1865AD, as the Bishopric of Aberdeen and Orkney.

Uniquely, St. Magnus Cathedral belongs to the people of Kirkwall. When Rögnvald was funding its construction, money ran short, and he was forced to raise extra funds by coercing the local population into buying back a set of rights that had been seized from them. In this way, the cathedral became their property, and despite periods during which this has been contested, it remains legally owned by the residents of Kirkwall to the present day.

Today, St. Magnus Cathedral survives as a stunning example of a Norman cathedral, unique in Scotland, and also the northernmost cathedral in the British isles. It dominates the Kirkwall skyline, and is easily the most impressive medieval building on Orkney. The sandstone fabric has weathered in a way that adds character and charm to the building's appearance, and the gentle and warm colours of the interior lend an atmosphere of gentle contemplation. When the sea winds are blowing strong outside its walls, the cathedral provides a palpable sense of sanctuary. Undoubtedly one of the many gems that makes travelling to Orkney a pilgrimage rather than just a journey.