His design, Happy Street, imagines the dark space beneath the old railway bridge in Wandsworth transformed into a welcoming space for pedestrians and cyclists, which the local community can also be proud of.
He plans to install enamel-powder-coated panels across the bridge's water-stained brick walls, creating a new surface that is both durable and reflective.
Both these panels, as well as the underside of the bridge, will be decorated in a rainbow of colours. These were selected by Illori to reference the bright colours that can be observed during sunsets over the River Thames nearby.
At night, the design will be illuminated by coloured lights "to bring a sense of cheerfulness and delight to a hitherto ordinary environment".
The project is set to go ahead, to be unveiled during the London Festival of Architecture (LFA) in 2019.
Ilori said he "can’t wait to work with the community to bring Happy Street to life".
"I am very grateful to the LFA team and the local community around Thessaly Road for believing in Happy Street and am looking forward to bringing the rainbow to the underpass," he said. "This is a very special project with a very special community and I feel honoured to have been given this opportunity."
Ilori's proposal was selected by a panel of judges that included Dezeen editorial director Amy Frearson, designer Morag Myerscough, LFA director Tamsie Thompson, head of culture for HS2 Anne Mullins, Footwork founder Clare Richards and Covent Garden Market Authority chair Pam Alexander.
It was also the most popular design in a local community vote.
Steffi Sutters, a Wandsworth Council cabinet member, described it as "a hugely exciting project to improve and rejuvenate a local thoroughfare".
"As well as bringing innovative art and colour to the street that will be enjoyed by all, I know that the local schoolchildren will be very happy with Yinka's bright design as they find the underpass dark and scary in its current state," she said.
"I'm really looking forward to seeing the design come to life over the next year and thank all the local residents who took part in helping us to get this far."
Illori often works with communities in his projects. In a recent project, he worked with people in addiction recovery to upcycle discarded chairs.
The London-based artist plans to work with the Wandsworth community to further develop his design before it becomes final.