Samsung's heir apparent Lee Jae-yong has been placed under arrest in South Korea, accused of bribery and other charges.
The case is linked to a scandal that led to the impeachment of President Park Geun-hye.
Samsung is accused of giving donations to non-profit foundations operated by Choi Soon-sil, a friend of Ms Park, in exchange for government favours.
Mr Lee and the Samsung Group deny any wrongdoing.
The acting Samsung chief was first questioned by prosecutors in January, but they decided then not to arrest him.
But he was questioned for a second time earlier this week.
On Friday, the court said it "acknowledged that it is necessary to arrest [Lee Jae-Yong] in light of a newly added criminal charge and new evidence."
The prosecution will now investigate further, and has 20 days to file formal charges. The arrest does not reflect a court opinion on guilt or innocence but only means it considers the potential crime very serious or that it assumes a flight risk.
What's the accusation?
Prosecutors accused Mr Lee of giving donations worth 41bn won ($36m;£29m) to organisations linked to Ms Park's close friend Ms Choi. They alleged this was done to win government support for a big restructuring of Samsung that would help a smooth leadership transition in favour of Mr Lee, who is standing in as chairman for his ill father, Lee Kun-hee.
The controversial merger required support from the national pension fund - the allegation is that this support was granted in return for the donations.
In a December parliamentary hearing, Samsung admitted giving a total of 20.4bn won to two foundations, but denied seeking favours in return.
Mr Lee also confirmed the firm gave a horse and money to help the equestrian career of Ms Choi's daughter, Chung Yoo-ra, something he said he now regrets.