The 22-year-old qualified fastest for the final with a Games record time of 1 min 13.05sec and then went on to better it by 0.43 seconds to secure top honours. 

Alonso Morales led on the turn and never looked back as Great Britain’s Bethany Firth came second in 1:12.89 and world champion Magda Toeters of The Netherlands took bronze in 1:17.35.

"I didn’t think it would be that hard," said the Spaniard. 

"It makes the four years of training and pain and injuries worth it."

In the first final of the evening, Alonso Morales' compatriot and world silver medallist Oscar Salguero Galisteo took gold in the men’s 100m breaststroke SB8 with a time of 1:11.11.

Italy’s Federico Morlacchi picked up his third medal of the Games with silver in 1:12.68, while Austria’s Andreas Onea held off a charge from the United States' Dalton Herendeen to claim bronze in 1:14.44.  

A third gold came for Spain in the men’s 100m butterfly S11, courtesy of world bronze medallist Israel Oliver.

It was not easy, however, as the top four finished within 1.5 seconds of each other. 

Third on the turn, Oliver pushed hard for gold in 1:02.24 as world champion Keiichi Kimura of Japan took silver in 1:02.43 and Ukraine’s Oleksandr Mashchenko came third in 1:03.38.

Also shining on the big stage this evening was Paralympic debutant Anna Stetsenko, with the Ukrainian breaking a 20-year-old world record in the women’s 50m freestyle S13.

The European champion powered to the wall in 27.34, beating the mark of Germany’s Yvonne Hopf - set at the Atlanta 1996 Paralympics - by 0.04 seconds.

Uzbekistan's Muslima Odilova was the runner-up in 28.00, while fellow countrywoman Shokhsanamkhon Toshpulatova rounded out the podium in 28.02.

Having lowered the world record in the men’s 50m breaststroke SB2 heats, China’s Huang Wenpan reduced it again in the final to ensure victory in 50.65. 

Huang led an-all Chinese top three with Li Tingshen the runner-up in 51.78 and Huang Chaowen the bronze medallist in 54.29.

His world record was swiftly followed by another for China in the men's 50m breaststroke SB3 final as Jin Zhipeng bettered the 48.49 set by Japan’s Takayuki Suzuki at Beijing 2008 with a time of 47.54. 

Spain’s Miguel Luque was second in 49.47, while Italy’s Efrem Morelli took bronze in 49.92.

Cheng Jiao secured China’s third gold medal with a time of 58.28 in the women’s 50m breaststroke SB3 final, pulling away from Ukraine’s Mariia Lafina, who finished second in 1:01.92, and Mexico’s Patricia Valle, the bronze medallist in 1:02.40.

Britain’s Hannah Russell was another star performer this evening, setting a world record time of 1:06.06 en route to winning the women’s 100m backstroke S12.

The 20-year-old lowered her own mark from last year to beat nearest challenger Yaryna Matlo of Ukraine by 5.91 seconds and Spain’s Maria Delgado Nadal by a further 0.76 seconds.

Today’s action was capped off with a thrilling men's 4x100m freestyle relay 34 points final, which was won by Ukraine in a Paralympic record time of 3:48.11.

Hosts Brazil claimed silver in an Americas record time of 3:48.98 with a great anchor leg from Phelipe Rodrigues ensuring they finished ahead of China, third in 3:50.41.

For a full set of results, check out our live blog here.