The 2007–08 National Division Three South was the eighth season of the fourth division (south) of the English domestic rugby union competition using the name National Division Three South. New teams to the division included Barking who were relegated from the 2006–07 National Division Two while promoted sides included London Scottish (champions) and Ealing (playoffs) who came up from London Division 1, Mounts Bay who came up as champions of South West Division 1 and Luton who were Midlands Division 1 champions. In the case of Luton, Midlands league champions usually moved up to National Division Three North but due to number imbalances in that division, for this season, they would go into National Division Three South instead. The league system was 4 points for a win, 2 points for a draw and additional bonus points being awarded for scoring 4 or more tries and/or losing within 7 points of the victorious team. In terms of promotion the league champions would go straight up into National Division Two while the runners up would have a one-game playoff against the runners up from National Division Three North for the final promotion place.