Her Majesty will hit the start button from the grounds of Windsor Castle at 10am on Sunday 22 April to set athletes including Sir Mo Farah off on the 26.2-mile course around the capital.
It is thought 40,000 runners will participate in the iconic races, which runs from Blackheath to The Mall.
"We are deeply honoured that Her Majesty The Queen has accepted the invitation to start the 2018 London Marathon, especially as this will happen 110 years after the 1908 Olympic Marathon was started at Windsor Castle by the then Princess Mary, grandmother to The Queen," said Sir John Spurling, chairman of London Marathon Events.
That marathon was the first to be held over the now-traditional 26.2-mile distance, when Princess Mary – later Queen Mary – set runners on their way from Windsor Castle.
This year, Daniel Wanjiru from Kenya, who won last year's race, will lead a strong men's elite field which also includes Sir Mo, Rio Olympic champion Eliud Kipchoge and Britain's Aaron Scott.
Meanwhile, the women's elite field boasts the talents of three-time London champion Mary Keitany as well as Brits Lily Partridge and Charlotte Purdue, the latter of whom has just been named captain for this weekend's World Half Marathon Championships in Valencia.