Jose Fonte's second-half strike saw Southampton extend their unbeaten run to six Barclays Premier League matches at Hull, who remain within touching distance of the relegation scrap.
Saints were good value for three points, maintaining a fierce tempo throughout at the KC Stadium and creating a host of fine chances.
Rickie Lambert and Jay Rodriguez were both in profligate mood, raising Hull's hopes of a battling draw, but Fonte settled things in the 69th minute when he stabbed over the line at the second attempt.
The Portuguese defender needed the Goal Decision System to claim the goal, with Lambert rifling home on the follow-up after Maynor Figueroa tried in vain to clear the danger.
Lambert had earlier missed a pair of wonderful chances in the opening seven minutes, while Rodriguez struck the crossbar from 20 yards.
Hull were far from passengers in the contest, striking the woodwork first when Shane Long's header kissed the inside of the post, but they could not match Saints' energy around the park and tired visibly as the game progressed.
Having taken four points from Tottenham and Sunderland this month, their attempts to pull clear of the strugglers were duly stalled.