J Mascis + The Fog was an American rock band formed by J Mascis in 2000, following the break-up of Dinosaur Jr. The project released two albums; 2000's More Light and 2002's Free So Free.

Joseph Donald Mascis Jr., better known as J Mascis, is an American musician who is the singer, guitarist and main songwriter for the alternative rock band Dinosaur Jr. He has also released several albums as a solo artist and played drums and guitar on other projects. He was ranked number 74 in a Rolling Stone list of the "100 Greatest Guitarists", and number 5 in a similar list for Spin magazine in 2012.