At 6ft 4in tall and weighing 17st 9lb, the 24-year-old Mapapalangi is a physical presence in attack and defence from the back row and has gained experience in New Zealand with Auckland, Waikato, Chiefs and Manawatu.
"Valentino is a very talented young player with a lot of potential to grow and develop with us."
Tigers head coach Matt O'Connor
An exciting talent in Tongan rugby, he earned his first international selection during 2016 and started the Test against Wales this summer.