Graham Hughes, 33, accomplished the feat when he arrived Monday in South Sudan, a country that did not yet exist when he began his quest Jan. 1, 2009, The Daily Telegraph reported.
Hughes said he had filled four full passports by the time he visited all 193 United Nations member states, as well as Taiwan, Vatican City, the Palestinian territory, Kosovo, Western Sahara and the four home nations of Britain.
Guinness World Records said Hughes' travels were a record because he did it without flying.
"The main feeling today is just one of intense gratitude to every person around the world who helped me get here, by giving me a lift, letting me stay on their couch or pointing me in the right direction," Hughes said. "There were times, sitting in a bus station in Cambodia at one in the morning, riding some awful truck over bad roads, when I thought, why am I doing this? But there was always a reason to keep going."