Tasiusaq Bay (Danish: Vakkerprydsbugt) is a bay in the Upernavik Archipelago in the Avannaata municipality in northwestern Greenland. It is an indentation of northeastern Baffin Bay. The name of the bay derives from the name of the settlement of the same name in the bay.

The bay is located in the north-central part of Upernavik Archipelago, between Sugar Loaf Bay in the north, and Upernavik Icefjord in the south. At its widest − from the Cape Shackleton promontory on Apparsuit Island in the north at 73°48′13″N 56°49′57″W / 73.80361°N 56.83250°W / 73.80361; -56.83250, to the mouth of Upernavik Icefjord in the south − Tasiusaq Bay stretches for approximately 93 km (58 mi).

There is a large number of islands and skerries in the bay, scattered over the entire area. They can be divides into several groups:

The northernmost group of islands lies between the Nasaussap Saqqaa fjord emptying into Sugar Loaf Bay in the north, and the Kangerlussuaq Icefjord in the south. The major islands, listed from north to south, are:

The central group of islands lies between the Kangerlussuaq Icefjord in the north, and the mouth of Upernavik Icefjord in the south. The major islands, listed from north to south, are:

The southern group of islands bounds the Upernavik Icefjord from the north. The major islands, listed from east to west, are:

The coastline of mainland Greenland in the region is a series of alternating nunataks and glaciers draining the Greenland ice sheet (Greenlandic: Sermersuaq). the major features, from north to south, are:

The major waterways of Tasiusaq Bay are the Nasaussap Saqqaa fjord in the north, Kangerlussuaq Icefjord, and Upernavik Icefjord in the south.