Sinckler has represented England at under-16, under-18, under-19 and under-20 levels, and has been a crucial member of the senior team since 2016, in which he has won the Six Nations Championship, the Calcutta Cup and the Millennium Trophy. Sinckler's performances for England led to him being include in Warren Gatland's squad for the British &amp; Irish Lions' tour to New Zealand in 2017. In 2019, he was a member of the England squad that finished as runners-up to South Africa at the Rugby World Cup in Japan, though picked up injury during the final.