Coat of arms of Oslo

Oslo is one of very few cities in Norway, besides Bergen and Tønsberg, that has no formal coat of arms, instead using a city seal. However, the Seal of Oslo is officially regarded by the city government as its coat of arms. It depicts the city's patron saint, St. Hallvard. The seal shows St. Hallvard with his attributes, the millstone and arrows, with a nude woman by his feet. He is seated on a throne with lion decorations, which at the time was also commonly used in the seals of Norwegian kings. Around the circular image the city's motto is inscribed: Unanimiter et constanter (United and constant).

The oldest known seal of Oslo showed the same composition as today's design, except that instead of a female figure reclining at the feet of St. Hallvard, there was an armed warrior; one of the evil men who killed Hallvard, but was defeated by the saint. This seal was probably introducd around 1300 and was in use for nearly three centuries. Due to its bad state of preservation, the image was later misinterpreted as the woman whom Hallvard tried to defend. After the Reformation, the city continued to use the seal with the image of St. Hallvard. The second seal of Oslo dates from around 1590. It shows the same basic design, but the saint holds his attributes in the opposite hands. Also the stars and some other smaller details were lost. This seal was used until around 1660.

At that time the city of Oslo had been destroyed in the fire of 1624, and King Christian IV ordered its relocation across the bay and renamed it Christiania. The Cathedral Church of St. Hallvard barely survived the fire, but was later abandoned and used as a quarry. By 1660 it had become a ruin, and the legend of St. Hallvard was no longer well known. The third seal made in 1659, now that of the relocated city of Christiana, still showed the same basic design, but the saint was transformed into a female figure, probably now perceived as an embodiment of Christiania. She still held the arrows and had a dead knight (with harness and helmet) lying at her feet. The millstone had become thinner and looked more like a ring. A new feature of this seal was the motto of the city surrounding the circular motif,

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