OsmAnd is a powerful open-source navigation app built on OpenStreetMap that works entirely offline. It is endlessly configurable — with specialised modes and plugins for skiing, sailing, off-road, cycling and more — which makes it the power-user's choice among privacy-friendly map apps.
Free, open-source and tracking-free, OsmAnd is a deep, capable European alternative to Google Maps for anyone willing to trade a little polish for total control and offline reliability.