Ryan, 72, sat stone-faced as the verdict was read and afterward vowed to appeal.
"I believe this decision today is not in accordance with the kind of public service that I provided to the people of Illinois over 40 years, and needless to say I am disappointed in the outcome," Ryan said.
Ryan faces up to 20 years in prison for racketeering conspiracy charge alone, the most serious against him in the 22-count indictment. The jury also found him guilty of fraud, obstructing the Internal Revenue Service and lying to the FBI.
Co-defendant Larry Warner, a Chicago businessman and Ryan friend, was also found guilty of racketeering conspiracy, as well as mail fraud, attempted extortion, illegally structuring bank withdrawals and money laundering.
Neither man took the stand during their six-month trial.
Prosecutors accused Ryan of steering big-money state contracts and leases, including a $25 million IBM computer deal, to his friends and political insiders while he was secretary of state in the 1990s and then as governor starting in 1999.
In return for that help, he was rewarded with annual winter vacations in Jamaica, stays in Cancun and Palm Springs and gifts ranging from a golf bag to $145,000 in loans to his brother's business, prosecutors said.
Warner, 67, was one of those beneficiaries and raked in $3 million from Ryan-era deals, according to the office of U.S. Attorney Patrick Fitzgerald — who during the trial was also leading the federal investigation into the leak of CIA officer Valerie Plame's identity.
"There was just too much evidence, from too many witnesses, pointing too many fingers at Ryan and his colleague for either defense team to have been able to portray it as a coincidence or a witch hunt or anything short of widespread corruption," says CBS News legal analyst Andrew Cohen. "And that's why we see this verdict."
The case against the Ryan and Warner was the state's biggest political corruption trial in decades, and it had it share of troubles.
Late last month, six months of arguments and testimony nearly went down the drain when the judge discovered two jurors had failed to mention past arrests on their court questionnaires.
The new jury had deliberated for 10 days when it announced its verdict.
The corruption scandal that led to Ryan's downfall began over a decade ago with a much smaller focus: a federal investigation into a fiery van crash in Wisconsin that killed six children.
The deadly 1994 crash exposed a scheme inside the Illinois secretary of state's office in which unqualified truck drivers obtained licenses for bribes. Ryan was secretary of state at the time, and prosecutors would later argue that thousands of dollars in payoff money from the licenses went into a Ryan campaign fund.
The probe expanded over the next eight years into a wide-ranging corruption investigation that eventually reached Ryan in the governor's office.
Seventy-nine former state officials, lobbyists, truck drivers and others have been since charged. Before Ryan's trial, 74 had been convicted, including Ryan's longtime top aide, Scott Fawell.
Fawell was a star witness against Ryan and the author of a 1994 memo that lead prosecutor Patrick Collins called "the Magna Carta" of the racketeering scheme.
The memo urged Ryan, then-secretary of state, to replace inspector general Dean Bauer with someone who "won't ask about FR tickets" — political fundraising tickets. Bauer himself pleaded guilty to obstruction of justice and acknowledged the government could prove he had spent seven years covering up scandals to spare Ryan personal and political embarrassment.
Even as he faced federal charges back home, Ryan accepted speaking invitations across the country and was nominated for the Nobel Peace Prize for his criticism of the death penalty.
In 2000, the Republican governor declared a moratorium on executions in Illinois after 13 death row inmates were found to have been wrongly convicted. Then, days before he left office in 2003, he cleared death row, commuting the sentences of all 167 inmates to life in prison. He declared that the state's criminal justice system was "haunted by the demon of error."
The auto accident that set the case in motion killed six children of the Rev. Scott and Janet Willis. The truck driver took the Fifth Amendment when asked in a lawsuit how he got his license, but a trucking company official later said he believed the license was one of several he bought from a state official.
The Willises, who received a $100 million settlement, attended parts of the Ryan trial.
Ryan's sentencing was scheduled for Aug. 4.