R. Timothy Ziemer (born 1946) is an American retired naval officer. He was a U.S. Navy helicopter pilot in the Vietnam War, commanded several squadrons and an air wing during the First Gulf War, and completed his Navy career as commander of the Navy's Mid-Atlantic Region, with the rank of rear admiral. After retiring he became an expert in global disaster response and health threats. He led the President's Malaria Initiative from 2006 until 2017, then joined the National Security Council as the director in charge of global health security and biothreats, serving until May 8, 2018, when the position was abolished by the Trump administration.