Wainaina is a surname. Notable people with the surname include:
Angel Wainaina (1983–2009), Kenyan actress, radio presenter and rapper Anthony Wainaina, Kenyan MP Binyavanga Wainaina (1971–2019), Kenyan writer Catherine Wainaina (born 1985), Kenyan beauty pageant winner Eric Wainaina (musician) (born 1973), Kenyan singer-songwriter Erick Wainaina (born 1973), Kenyan marathon runner Fidelis Wainaina, Kenyan activist Njoki Wainaina