Lysaker is an area in Bærum Municipality, Viken County, Norway. Lysaker is the easternmost part of Bærum and borders Oslo proper. Lysaker was initially a farming community, later becoming a residential area. Today it is primarily known as a business and trade area, and a public transport hub. It is considered part of Stor-Oslo (Greater Oslo), and is home to offices of numerous domestic and international businesses.
Lysaker is located where a stream, Lysakerelva, empties into Lysakerfjorden—a branch of the Oslofjorden. This stream is the western border of Oslo proper.