A South Korean court has sentenced Kim Seung-youn, chairman of the Hanwha group, to four years in prison for embezzlement.
The court said Kim had failed to show any remorse for using his position to benefit himself and his family, causing the company financial losses.
His sentence included a fine of 5.1bn won ($4.5m, £2.8m). A Hanwha spokesman said he would appeal against the verdict.
Kim was taken into custody immediately.
The move to send him straight to prison was seen as unusual, as previous cases involving top business officials had led to suspended sentences.
"We did not expect that Chairman Kim would actually be imprisoned," a Hanwha official was quoted as saying by Yonhap news agency.
The court said that Kim used Hanwha affiliates to "unfairly support" companies that he owned. It also said he used his influence to help companies run by his brother.
"Chairman Kim incurred losses to the company by taking advantage of his influence as the Hanwha Group's major shareholder," the court said.
Kim was convicted in 2007 for abducting and assaulting workers in a karaoke bar, but his sentence was eventually suspended.
Hanwha is one of the largest business conglomerates in South Korea. It has 53 subsidiaries that span manufacturing, construction and finance companies.