The senator was also a stalwart supporter of arming Kyiv and applying sanctions against Moscow. Zelensky said in a post on X, external that he was “deeply saddened” by his death.
“America and the world have lost a determined leader,” he added.
Graham had a difficult time as a young adult. While in university, he lost his mother and father within two years of each other. He went on to help raise his younger sister and ultimately legally adopted her.
After finishing university, he graduated from law school and joined the US Air Force as a military prosecutor and defence attorney before becoming a US senator.
South Carolina Governor Henry McMaster now has the power to appoint a temporary replacement for Graham until the end of his current term in January.
His successor will be chosen in November’s midterm elections.
Before Graham’s death, Republicans held a 53-47 majority over Democrats in the Senate. Both parties are fighting for Senate control in November.
The death comes as another Republican senator has been hospitalised for weeks with an unknown medical condition. Aides to Kentucky Senator Mitch McConnell have released few details about his condition.
