Ferromagnetism in half-metallic two-dimensional materials can lead to unique spintronics applications.Here we report frst-principles calculations that predict monolayer graphyne nanoribbons(GyNRs),an alternative to graphene,doped randomly with 3d-series transition metal atoms at high concentrations are ferromagnetic(FM)with Curie temperatures above room temperature.Furthermore,Cr-,Fe-and Co-doped GyNRs are half-mettallic with 100%spin polarization at the Fermi level and can act as perfect spin flters.The high spin polarization of the current is preserved up to large bias voltages.This study provides a basis for the fabrication of GyNRs with high Curie temperature and spin-polarized electron transport properties.