Bilyan (af-ingiriis: Billion, af-carabi مليار) waa tiro xisaabeed oo ka kooban toban god. Tusaale ahaan, hal Bilyan waa 1'000'000'000. Tiroda Bilyan waxa ka sareeya ama ka badan Tiriliyan oo ka sameeysan sadex-iyo-toban god (hal tiriliyan = 1'000'000'000'000) waxaana ka hooseeya Bilyanka tirada loo yaqaano Milyan oo ah todoba god (hal milyan = 1'000'000).