The president says the guilty verdict shows the Iraqi people are replacing the rule of a tyrant with the rule of law.
"It is a major achievement for Iraq's young democracy and its constitutional government."
In a brief statement to reporters, Mr. Bush said Saddam Hussein's victims have received a measure of justice, which many thought would never come.
Saddam was sentenced to hang. He has 30 days to appeal.
Mr. Bush emphasized the completion of the first of Saddam's two war crimes trials shows progress is being made.
"Iraq has a lot of work ahead, as it builds a society that delivers equal justice and protects all its citizens. Yet, history will record today's judgment as an important achievement on the path to a free and just and unified society."
The president spoke as he prepared to leave an airport near his Texas ranch to campaign for Republican candidates in the final days before Tuesday's national election in the United States.
The war in Iraq has become a key issue for the electorate that observers say could put Democrats in control of one or both houses of Congress. But President Bush indicated he is not planning a change in policy, no matter who wins at the polls.