Lea Fastow, whose husband Andrew was sentenced to ten years in jail for his role in the collapse of Enron, has begun a year's prison term of her own.
Lea Fastow (left) was Enron's assistant treasurer until 1997
Mrs Fastow, 42, reported to a jail in Houston, only a few miles away from her home in the Texas city.
She was convicted of helping her husband, Enron's former chief financial officer, hide money from financial schemes set up before Enron's collapse.
Mr Fastow was indicted on 98 counts of conspiracy, fraud and insider trading.
It is likely that the couple, who have two children under the age of five, will serve their terms independently of each other.
Fastow pleaded guilty to two counts of conspiracy to defraud in January.
He agreed to co-operate with the US Justice Department to help bring a prosecution against Enron executives including former chairman Ken Lay in return for a reduced sentence.
Mr Lay was recently indicted on 11 charges of bank fraud, share trading fraud and making false statements. If convicted of all counts, he could face up to a maximum 175 years in jail.
Mr Fastow is expected to be the chief prosecution witness in a future trial, which has yet to be scheduled.
Mrs Fastow was Enron's assistant treasurer until 1997.
Mike DeGuerin, her attorney, told reporters outside the Federal Detention Centre that he believed the sentence was "wrong and unjust".