Trump -- almost certain to be the Republican presidential nominee this November -- was found liable for unlawfully inflating his wealth and manipulating the value of properties to obtain favorable bank loans or insurance terms.
Trump accused President Joe Biden of driving the case, calling it "weaponization against a political opponent who's up a lot in the polls", and vowed to appeal.
As the case was civil, not criminal, there was no threat of imprisonment. But Trump said ahead of the ruling that a ban on conducting business in New York state would be akin to a "corporate death penalty."
Trump, facing 91 criminal counts in other cases, has seized on his legal woes to fire up supporters and denounce his likely opponent Biden, claiming that court cases are "just a way of hurting me in the election."
However, Judge Arthur Engoron said the financially shattering penalties are justified by Trump's behavior.
"Their complete lack of contrition and remorse borders on pathological," Engoron said of Trump and his two sons, who were also defendants, in his scathing ruling.
"They are accused only of inflating asset values to make more money... Donald Trump is not Bernard Madoff. Yet, defendants are incapable of admitting the error of their ways," he added, referring to the perpetrator of a massive Ponzi scheme.
Trump's sons Eric and Donald Trump Jr. were also found liable in the case and ordered to pay more than $4 million each, prompting Don Jr. to claim on social media that "political beliefs" had determined the outcome.
The Trump Organization, an avowedly family business, will also be forced by the ruling to allow in an independent compliance director answerable to the court.
'Tremendous victory'
It was as a property developer and businessman in New York that Trump built his public profile which he used as a springboard into the entertainment industry and ultimately the presidency.
The judge's order was a victory for New York state Attorney General Letitia James. She had sought $370 million from Trump to remedy the advantage he is alleged to have wrongfully obtained, as well as having him barred from conducting business in the state.
"This is a tremendous victory for this state, this nation, and for everyone who believes that we all must play by the same rules -- even former presidents," James said.
Trump has repeatedly attacked James, calling her a "lunatic," as well as smearing Engoron, who decided the case without a jury, calling him "out of control."
During highly technical testimony, the court heard that in one case Trump valued Mar-a-Lago, his exclusive Florida club, by using "asking prices," rather than actual sales prices, for a comparison.
"From 2011-2015 defendants added a 30 percent premium because the property was a 'completed (commercial) facility,'" the prosecution said, arguing it unlawfully distorted its true value.
Trump's lawyer Chris Kise said "there is no clear and present evidence establishing intent by Donald Trump."
Kise acknowledged there could be errors in Trump's corporate financial statements but none "lead to the conclusion there was fraud."
Legal whirlwind
The ruling caps a whirlwind legal week for Trump.
Trump appeared in a New York court Thursday ahead of a criminal trial, where he faces charges of illegally covering up hush money payments. It will be the first criminal trial of a former U.S. president.
Trump's lawyers were also representing him in Atlanta, Georgia, where he is accused of conspiracy to overturn the 2020 election, which he lost to Biden.
A separate trial on Trump's attempts to overturn the 2020 election is on hold in Washington, DC, while Trump attempts to assert presidential immunity.
The twice-impeached former president is due to go on trial in Florida in May on charges of taking troves of highly secret documents when he left the presidency and thwarting officials trying to recover them.
