The invention relates to a single-use connection device for insertion into a connection opening of a bioreactor, in particular in a connection opening of a top plate of a dimensionally-stable bioreactor or in a connection opening of a connection element of a pouch bioreactor. The single-use connection device is inserted in a connection opening of a top plate of a bioreactor and/or in a connection opening of a pouch reactor and is provided with multiple passages and an attachment section, wherein the single-use connection device is formed as a single piece and is made of plastic. The attachment section, on an outer peripheral surface, has an attachment structure for attaching the single-use connection device in the connection opening.