It was Mourinho himself who approved Calafiori's sale for just £1.5m when the Italian was at Roma four years ago.
The Mirror reports that the new Real Madrid head coach, who agreed a three-year deal at the Bernabéu last month, is keen to test Arsenal's resolve over a player they purchased from Basel for £42m in the summer of 2024.
Mourinho has already secured agreements for Inter Milan right-back Denzel Dumfries and Liverpool centre-back Ibrahima Konaté, and now wants a third defensive addition.
Calafiori joined AS Roma as a teenager from Bologna's academy and made his debut under Mourinho in 2021. The Portuguese coach sanctioned his sale to Basel in January 2022 for £1.5m as part of a squad clear-out, after which the 23-year-old's development accelerated rapidly. He joined Bologna in 2023, had a season of exceptional form that earned him a move to Arsenal in a deal worth £42m, and won the Premier League title in his debut campaign at the Emirates Stadium.
Arsenal regard Calafiori as a valued squad member. He can operate as a left-back or left-sided centre-back and has formed a useful complement to the club's established defensive options.
However, he was the one left out of the starting lineup for the Champions League final against Paris Saint-Germain, partly due to injury, and has been behind Piero Hincapié and Myles Lewis-Skelly in recent selection decisions.
Whether Mourinho's interest produces a formal bid, and whether Arsenal would contemplate selling to a direct Champions League rival, remains to be seen. The player is a regular with Italy and fully committed to the new season.