The Hollyoaks star, 36, and Riad, 38, started dating last year, but according to sources split this week – just a day after returning from a holiday to Dubai.
An insider told The Sun: "They weren't getting on and the holiday was the final nail in the coffin.
"Sadly they have parted ways due to busy schedules. It has ended amicably and Steph wishes him well."
Last night Stephanie appeared to send a subtle message following her split from Riad.
She stepped out with fashion designer friend Nadine Merabi, who wore a t-shirt emblazoned with the slogan 'No boyfriend, no problems'.
Early last year Stephanie split from personal trainer Dan Hooper, who she shares daughter Lexi with.
Dan is now engaged to Coronation Street star Kym Marsh, who has also been linked to businessman Riad in the past.
Riad has a son, Alfie, with Atomic Kitten singer Natasha Hamilton.