Jessie J is a pseudonym of, at least, two artists:
1. A singer songwriter from the United Kingdom
2. A rapper from the United States
1. Jessie J (born Jessica Cornish on 27 March 1988) is a singer-songwriter from Essex, England, United Kingdom. She began a solo career after working as a songwriter and backing vocalist for artists such as Miley Cyrus and Christina Aguilera. Her debut album, "Who You Are", was released in 2011 and contains the singles "Do It Like A Dude", "Price Tag", "Nobody's Perfect", "Who's Laughing Now", "Domino" and "Who You Are".
Sites: Discogs & MusicBrainz.
2) Jessie J. Chambers Jr., better known as Jessie J is an American record producer, writer, and rapper. Jessie J is a Life Music recording artist out of Orlando, Florida currently working on his new album.