Wikipedia
OsmAnd
OsmAnd (OpenStreetMap Automated Navigation Directions) is a free and open source, global mobile map viewing & navigation app for offline and online maps for Android and iOS. It uses the OpenStreetMap (OSM) map database for its primary displays. The development of this project is being done on GitHub and the Android version is available under the GPLv3 license. The application is available in both a free and a paid version which works as a donation to the developer, unlocks the download limit for offline maps, and provides access to Wikipedia POIs and their description from within the app.