The singer, due to release his second solo album later this year, allegedly hit his fiancée Samantha Millar - who is also the mother of his son.
BBC News reports that the attack is alleged to have happened while the pair were in a car in London's West End on Wednesday.
A Metropolitan Police spokesman said: "Lee Ryan, self-employed, of Henley-on-Thames, is due to appear on bail charged with common assault."
The Blue star is due to appear at City of Westminster Magistrates' Court on August 27.
His most recent Twitter update, posted on Wednesday, read: "Looking forward to going to disney land with sammi and baby!!! X"