Shizuo Akira (born January 27, 1953, in Higashiōsaka) is a professor at the Department of Host Defense, Osaka University, Japan. He has made ground-breaking discoveries in the field of immunology, most significantly in the area of innate host defense mechanisms.

Besides being one of the world's most-cited scientists, he has also been recognised, in the years 2006 and 2007, for having published the greatest number of ‘Hot Papers’ (11 papers) over the preceding two years. He is the recipient of several international awards, including the Gairdner Foundation International Award (2011), Robert Koch Prize, the Milstein Award (2007), and the William B. Coley Award.

Among his greatest discoveries is the demonstration, through the ablation of toll-like receptor (TLR)s genes, that TLRs recognize a discrete collection of molecules of microbial origin, and later the RNA helicases, RIG-I (retinoic-acid-inducible protein I) and MDA5 (melanoma differentiation-associated protein 5). All molecules belong to the pattern recognition receptors, which detects intruding pathogens and initiates antimicrobial responses in the host.