The new monument, located at West India Quay in the city’s Docklands, will also recognise the role London played in the trade.
Mr Khan has committed £500,000 to help create the memorial, expected to be unveiled in the summer of 2026.
The Mayor said: “The impact of the slave trade has been felt by generations of Black communities in London, across Britain and around the world. Despite this, we do not have a dedicated memorial in our capital to honour the millions of enslaved people who suffered and died as a result of this barbaric practice.
“I want everyone to be able to take pride in our public spaces and by being candid about our history, and its enduring legacy, we are creating a better and fairer London for all.”
The promise of creating such a memorial was made in Mr Khan’s 2021 re-election manifesto.
Speaking at the monument’s announcement event on Friday, Dr Debbie Weekes-Bernard – Deputy Mayor for Communities and Social Justice – said the artwork would be “an incredibly important initiative” for the city.
“The reason that its so important for London is that whilst we know that London as a city was very involved in the abolitionist movement, in the attempts to have the slave trade abolished, it’s also a city which was very heavily involved in the development of the slave trade,” she said.
“I think that there are lots of stories about different parts of our city and the relationship that those different parts had to the slave trade, that a lot of people don’t know about.
“We want to use this as an opportunity to open up that discussion, to enable us to learn more about the way in which that very dark period of our history is actually a part of London’s story, and bringing that centre-stage in the way we talk about London.”
The Commission for Diversity in the Public Realm, set up by Mr Khan, will develop an artistic brief for the memorial that will be informed by community engagement. An artist to design it will then be selected through an open competition.
“We’ve got a lot of talented artists out there, so I’m really excited to see what they come up with,” said Dr Weekes-Bernard.
The monument’s precise location at West India Quay has not yet been decided, but it will be close to where a statue of prominent London-based slave trader Robert Milligan once stood.
In 2020, the Canal and River Trust, the London Borough of Tower Hamlets, the Museum of London, and other partners in Canary Wharf, removed the statue, which had been in place since 1997. The statue is now part of the Museum of London’s collection and is being held in storage while the museum consults with the public on how to best present it.
Aside from the main monument, there are also planned to be a number of ‘satellite’ monuments, dotted across different London locations.
Dr Weekes-Bernard said City Hall did not currently “want to put a firm number” on how many ‘satellite’ sites there will be.
But she said her team would be working with the artist of the main memorial to determine their locations, which will be found in “some of those key places in London that have a really clear and interesting story to tell about the relationship between London and the slave trade”.
She added: “We want this to be something which is really artist-led, and community-led as well, because this has to be something that Londoners can get involved in, but then speaks to Londoners’ experiences and their expertise about the areas in which they live – so that it can tell both London’s story but also their story.”
The Deputy Mayor said she was also keen to involve the Memorial 2007 group, who have been separately campaigning for a national memorial sculpture for the victims of the slave trade to go in Hyde Park.