Olivier leapt to victory with a distance of 17.01m to equal his NZ Triple Jump record and his Oceania U20 record fresh off his Olympic debut in Paris.
"I'm very happy, I put in two weeks of hard work after coming back from the Olympics. I'm glad it paid off, I equalled my PB today so I'm very happy.
"I had supreme confidence I was going to win today…I was here to get a medal and I wanted to make sure that it was gold,"
In Lima, he entered the competition as the number one ranked athlete with a best over half a metre clear of the rest of the field.
The only challenge of the day came in the form of a third round attempt of 16.74 PB from eventual silver medallist, Karson Gordon of the USA.
"I took a far more relaxed approach to the U20 championships… I think I put a bit too much pressure on myself in Paris, so taking a more relaxed approach here has worked in my favour massively."
Olivier had a disppointing Olympics finishing 30th in the 32 strong field, with a best jump of 16.16 metres, 85cms off his personal best.
This victory in Lima is Olivier's second appearance at the World U20 Championships, where he finished in 4th in 2022.
Based in South Africa Ethan is coached by his father, Wikus, a former Commonwealth Games triple jump representative for South Africa. Olivier notes his father's triple jump prowess as a motivating factor for him gravitating towards the event.
"My father's success in triple jump was also a motivator and I strived to be as good as he was."
Olivier's win is the New Zealand's first male gold at the World U20 Championships since shot putter Jacko Gill's 2012 gold.
Gill recently finished 6th at the Paris 2024 Olympics.
Olympic shot put silver medallist Maadi Wesche won the women's World U20 Championships in 2018.