According to femalefirst.co.uk, Smith's last serious relationship was with actress Lily James. 

According to sources, the two had split up because of work commitments but had got back together during the lockdown. 

"Matt and Lily's break-up was mostly because their hectic schedules meant they could barely see each other. They kept the house together when they split because they were both barely around. But when lockdown began, they ended up isolating together. Being in the house and having no work and distractions has allowed them to reconnect and get back to a good place," a source was quoted as saying earlier. 

However, the parted ways after that and now Lily is now in a relationship with musician Michael Shuman.