Red-billed quelea closely related to the fodies ("Foudia"), a genus of six or seven species that occur on the islands of the western Indian Ocean. These two genera are in turn the sister clade to the Asian species of the genus "Ploceus". The following tree represents current insight of the relationships between the species of "Quelea", and their closest relatives. Interbreeding between red-billed and red-headed queleas has been observed in captivity. The red-billed quelea is a small sparrow-like bird, approximately long and weighing , with a heavy, cone-shaped bill, which is red (in females outside the breeding season and males) or orange
Cardinal quelea on its head. Gustav Hartlaub was the first to described the cardinal quelea, giving it the scientific name "Hyphantica cardinalis" in 1880, based on specimens that were collected by Emin Pasha near Lado in South-Sudan during 1879. In 1951, Hans von Boetticher regarded the cardinal quelea and red-headed quelea sufficiently different from the red-billed quelea to create a new genus "Queleopsis". Its name in Swahili is "kwelea kidari-chekundu". Molecular phylogeny indicates that ancestors of the quelea species might have originated in India and dispersed to Africa. Based on more recent DNA-analysis, the red-headed quelea forms a clade with the cardinal