Commander Kamau Mbugua was a Human Starfleet officer during the 2260s.
In the year 2267, Mbugua was serving as the first officer of the USS Defiant when it encountered the cloaked IKS Kretoq in the Alamedus system and was forced to chase after it. (ST - Seven Deadly Sins novella: The First Peer)
In 2268, Mbugua was still on the Defiant when it was lost in interphase. (TOS episode: "The Tholian Web"; VAN novel: What Judgments Come)