Harringtonine is a cephalotaxine alkaloid originally found in Cephalotaxus hainanensis Li; it exhibits antiviral and anticancer activities. Harringtonine immobilizes initiated ribosomes, inhibiting protein translation by binding the A site of the 60 S ribosomal subunit and preventing aminoacyl-tRNA binding. Harringtonine inhibits chikungunya virus infection, suppressing replication, RNA production, and viral protein expression. Alone, harringtonine downregulates production of Mcl-1, increases cleavage of PARP, and inhibits cell growth in acute promyelocytic leukemia (APL) cells. Additionally, this compound improves the efficacy of co-administered chemotherapeutic compounds, further inhibiting proliferation and inducing apoptosis in leukemia cells. Harringtonine and homoharringtonine isolated from Cephalotaxus hainanesis have exhibited significant antileukemia activity and are widely used in clinics in China.