The Arctic region is undergoing dramatic changes, in the atmosphere, ocean, ice and on land. The Arctic lower atmosphere is warming at more than twice the rate of the global average, the Arctic sea ice and Greenland Ice Sheet melt have accelerated in the past 30 years. Notable observed changes in the ocean include the freshening of the Beaufort Gyre, and 'Atlantification' of the Barents Sea and of the Eastern Arctic Ocean. Such profound environmental change is likely to have implications across the globe - it is often said, "What happens in the Arctic doesn't stay in the Arctic". Past work has indicated that Arctic amplification can, in principle, affect European climate and extreme weather, but a clear picture of how and why is currently lacking. The 2019 Intergovernmental Panel on Climate Change (IPCC) Special Report on Oceans and Cryosphere concluded "changes in Arctic sea ice have the potential to influence midlatitude weather, but there is low confidence in the detection of this influence for specific weather types". ArctiCONNECT brings together experts in climate dynamics, polar and subpolar oceanography, and extreme weather, in order to transform understanding of the effects of accelerating Arctic warming on European climate and extreme weather, through an innovative and integrative program of research bridging theory, models of varying complexity, and observations. It will (i) uncover the atmospheric and oceanic mechanisms of Arctic influence on Europe; (ii) determine the ability of state-of-the-art climate models to simulate realistic Arctic-to-Europe teleconnections; and (iii) quantify and understand the contribution of Arctic warming to projected changes in European weather extremes and to the hazards posed to society.