Rousseff, Brazil’s first woman president, could be impeached at the end of the trial and thus end 13 years of left-wing rule over Latin America's biggest nation.
As a result of the Senate's vote Rousseff must immediately cede power to vice-president-turned-enemy Michel Temer, who is not a member of her Worker’s Party (PT).
“Today Brazilians are waking up to a new political reality,” said FRANCE 24 correspondent Richard Tompsett from Rio de Janeiro.
The vote came after a nearly 22-hour debate in the Senate closed with an overwhelming 55-22 vote against Rousseff, with pro-impeachment senators breaking into applause and taking selfies on the chamber floor.
“Throughout the marathon debate that preceded the vote, senators came up one by one, making their arguments,” Tompsett said. “The tone was much more sombre than the raucous vote in the lower house last month."
Thursday’s vote came after a majority of Brazilian MPs voted to impeach Rousseff in the lower house last month.
The president and her supporters have blasted the votes as a coup orchestrated by the opposition, pointing out that accounting tricks have been used by all of Rousseff’s predecessors in the past without outcry.
Temer, from the centre-right PMDB party, was to take over as interim president and was preparing to announce a new government.
Who to trust?
Despite a clear vote against Rousseff in the Senate, Brazilians remained bitterly divided over what should happen to her in the future.
Tensions were plain to see outside Congress, where police erected a giant metal fence to keep apart small rival groups of demonstrators.
Riot police pepper sprayed a group of Rousseff supporters late Wednesday and pro- and anti-impeachment protesters also scuffled briefly in Rio.
The country has been rocked by recession and a corruption scandal surrounding state oil giant Petrobras, which reaches deep into the political and business elite.
Rousseff has not been named in the sprawling corruption probe, but she has been accused of shielding her predecessor and political mentor Luiz Inacio Lula da Silva.
Temer has not been accused of wrongdoing in the scandal either, but some of the top leaders of his PMDB party have. As vice president he also risks scrutiny over the accounting tricks that backfired on Rousseff, as well as for questionable financing for the 2014 election campaign.
The latest target of the Petrobras investigation was Senator Aecio Neves, in a sign of the corruption that has become part of Brazilian politics.
Neves narrowly lost to Rousseff in the 2014 presidential elections and was one of the senators who voted to impeach her on Thursday. The Supreme Court authorised a probe into his alleged bribe-taking and money laundering overnight.
"Brazil can now start to turn a new page,” Neves, who is just one of dozens of senators facing or who have faced criminal cases, said shortly before casting his ballot.
(FRANCE 24 with AFP)