Foster is set to jet out to Monaco after both clubs confirmed the completion of his switch to the Ligue 1 club, with whom he has penned a four-and-a-half-year deal.
"AS Monaco is pleased to announce the arrival of Lyle Foster from Orlando Pirates (South Africa)," read a statement on the French side's website.
"Born on September 3, 2000 in Soweto, the 18-year-old South African striker signs until June 2023. He first joins National 2, coached by David Bechkoura.
He will now join the likes of Lebogang Mothiba, Bongani Zungu, Keagan Dolly and Lebohang Phiri in the French top division, but will begin his journey with ASM's B side.
The Amajita star had been on two previous assessments with The Monégasques over the last 18 months, and was touted to complete his move upon his 18th birthday, in accordance with FIFA regulations.
Having turned 18 on September 3, Foster narrowly missed the July/August transfer window and thus waited until this month to finalise the deal.
The Noordgesig-born forward, who recently helped the SA Under-20 national team succesfully defend their COSAFA crown in Zambia, will now await his work permit before departing for Europe.
Pirates' head of youth Augusto Palacios has since expressed his pride in aiding in the growth of the youngster who graduated through the club's youth ranks.
“It is such an honour to see Lyle moving to a big club at such a young age. As a person who is passionate about youth development, this is the type of thing that makes the long hours all worth it,” Palacios told Bucs' website.
“Lyle came into my hands as a baby at 13 years old, now here he is on the verge of making the biggest move of his career.
"I would like to wish him the best of luck and also thank the Foster family for their active involvement in their childs’ development.
He added: “Let this move pave a way for more such transfers in the future. For all the boys who will be part of the Project X tour of 2019, let this be an eye opener of what is possible if you make use of the opportunity when it presents itself.”