The 17 year-old striker has been with the Hammers since Under-9s.
“It feels good to have signed my first professional contract,” Sowunmi told whufc.com. “Being a professional footballer is something I’ve thought about for so many years so for it to finally happen is such a great feeling.
“I’ve come through the age groups with players I’ve grown up alongside so to see all of us reach this point together is really special. Hopefully we can all keep pushing and improving with the U21s.”
Academy Manager Kenny Brown also said: “Elisha is another player who’s been with us since the pre-Academy days and we’re seeing a pattern.
"In both the 2023 FA Youth Cup-winning squad and this season’s Premier League Cup-winning team, there have been so many boys that have been with us since U9s. That doesn’t happen by accident."