"Fidel Castro is dead!" Trump tweeted.
In an official statement released later Saturday morning, Trump referred to Castro as a "brutal dictator" who "oppressed his own people" for decades.
"Fidel Castro's legacy is one of firing squads, theft, unimaginable suffering, poverty and the denial of fundamental human rights," Trump said in the statement.
He added: "While Cuba remains a totalitarian island, it is my hope that today marks a move away from the horrors endured for too long, and toward a future in which the wonderful Cuban people finally live in the freedom they so richly deserve."
Castro, whose health had been failing for years, was pronounced dead at 10:29 p.m. local time, his brother and current Cuban leader Raul Castro announced on state-run television.
"At 10:29 in the night, the chief commander of the Cuban revolution, Fidel Castro Ruz, died," Raul Castro said in the televised address. "Ever onward, to victory."
President Barack Obama has made efforts to normalize relations with Cuba over the past few years. He became the first sitting president to visit the Communist-ruled island since Calvin Coolidge in March. Obama's statement on Castro's death took a markedly different tone than the president-elect.
Trump frequently criticized Obama's Cuba policy on the campaign trail, but it's unclear how the president-elect will continue relations with the island country.
"Though the tragedies, deaths and pain caused by Fidel Castro cannot be erased, our administration will do all it can to ensure the Cuban people can finally begin their journey toward prosperity and liberty," Trump said Saturday.