South Tynesider Josef Craig must regroup after seeing the first Paralympics medal hope vanish in Rio tonight.
Hynd lowered his own world record to touch first in 4min 21.89sec and upgrade on the silver he won in London 2012.
Nineteen-year-old Sunderland ABC swimmer Craig, a gold medallists in S7 in the London Paralympics four years ago, finished up in sixth place in 4.39.04, seven seconds off a medal.
He has the 50m and 100m freestyle events to look forward to, though, as well as the 4x100m freestyle.
Hynd said: “I don’t think there has been a day where I have not thought about London and how disappointed I was not to get the gold so it makes it all worth it now.
“I’m so happy with the time. I wanted to go under 4:20 if I’m honest but a world record, I’m happy with that.
“I’ve worked so hard for that, I can’t wait to get on the podium and get my medal.”
Meanwhile, Dame Sarah Storey won her 12th Paralympic gold. The 38-year-old swimmer-turned-cyclist surpassed former wheelchair racer Baroness Tanni Grey-Thompson as the British female with the most Paralympic titles by winning the C5 3km individual pursuit in the velodrome.
The honour of Britain’s first medal of the XV Paralympics went to Megan Giglia, who won gold in the C1-2-3 3km individual pursuit moments prior to Storey.
Storey qualified in a world-record time of three minutes 31.394 seconds – more than 17 seconds quicker than Crystal Lane in qualifying.
She overtook her team-mate before the halfway point in the final to claim gold.