Oliver, 23, who has autism, was among 26 swimmers from Yorkshire who competed at the 2016 British Learning Disability Swimming Championships at the Wales National Pool, Swansea.
The competition, now in its 11th year, was hosted by MENCAP Sport and Special Olympics Great Britain - two national charities providing quality sporting opportunities for athletes with learning disabilities.
Competing against the top swimmers from around the UK, Oliver, who trains with Minsthorpe Marlins, took gold in both finals of the breaststroke sprints to become National Champion in the 25m short course and the 50m long course events.
Oliver had previously held the 25m breaststroke title from 2011-13 and, last year, was the 200m breaststroke champion.
This year saw Oliver’s first national win in the long course event.
“It looked a long way to swim in the Olympic length pool, but I swam my fastest all the way to the finish,” said Oliver.
It was a superb weekend at the championships where he also won a bronze medal in his third breaststroke race and finished fourth overall in the 50m backstroke with a new personal best time.