The high latitude regions have warmed faster than the global average in recent decades, leading to a dramatic decline in sea-ice extent and thickness. These sea-ice changes vastly impact the polar environment, ecosystem, and local communities - They bring about both risks and opportunities for human activities in polar regions, e.g., scientific missions, tourism, fisheries, shipping, natural resource exploitation and wildlife management. Sea-ice changes may also have an influence extending beyond the polar regions, e.g., in parts of northern mid-latitude continents. Sea-ice prediction on subseasonal-to-seasonal (S2S) timescales benefits society and is a hot topic being researched internationally. Thanks to the recent advances in High-performance computing, model development and initialisation methods, and the emergence of novel observations, the gap between potential and realistic sea-ice predictability is closing in some regions and seasons but still remains significant. The 4SICE project is managed by the Nansen Environmental and Remote Sensing Center in Norway and the Sun Yat-sen University in China. 4SICE aims to improve the capability of S2S sea-ice prediction by improving the model, improving the initialisation method, and using yet untapped observations. The research in the project mostly focuses on the Arctic region, but will also assess the Antarctic which receives less attention. 4SICE sea-ice predictions will support scientific and economic activities in the polar regions.