The 26-year-old Clare man represented Ireland at the Special Olympics World Games in 2003 and 2007.
William, who works in Lynch’s Centra on the Gort Road, Ennis, said he hoped his achievement would serve as a “good message and good example” to other people with disabilities.
Proud father Liam first took William for lessons.
He said: “I showed him the ropes. He only started in November. We got an old car and we drove it around the field.”
William then went out on the road with driving instructor, Anita McGuire.
She said: “William wanted to firstly become a safe driver and once he had achieved this high level of competency, he was then determined to get his full driver’s license first time. Of course it helped a great deal that William has a very ‘cool and calm personality’, in his own words he ‘doesn’t do pressure, pressure is only for tyres’.”
The achievement has also been hailed by the president of Down Syndrome Ireland. Pat Clarke said to the best of his knowledge, William is the first person in the Republic with Down Syndrome to hold a full driving license.
“For people with Down Syndrome it shows that if they persevere they will get to where they want to get to,” said Mr Clarke.
William won two gold medals, three silver and two bronze for gymnastics at the 2003 games in Dublin. Four years later in China he claimed six gold and one bronze medal.