Many were held at the luxury Ritz-Carlton hotel in Riyadh.
The news signalled that the three-month-old purge, in which dozens of top officials and businessmen were detained by investigators who said they aimed to seize some $100 billion of illicit assets, was drawing to a close, reported Reuters.
Among those detained was one of the desert kingdom's most high-profile and wealthiest men, Prince Al-Waleed bin Talal.
Prince Alwaleed bin Talal, one of the kingdom's top global businessmen, was released from the Ritz on Saturday.
A sweeping anti-corruption drive in Saudi Arabia has generated an estimated $106.7bn (£75.6bn) in settlements, the kingdom's attorney general has said.
He said he will continue investigating the 56, but provided no further details about their identities.
Saudi's celebrated crown prince Mohammed bin Salman was elevated to the position of crown prince in June 2017, replacing his cousin Mohammed bin Nayef - a move that had been widely expected and could shape the direction of the country for decades. "Now it is the moment to get back to the book". "The positives for the business are that from the face of it, it looks like it is business as usual for the companies".
The Saudi Arabian central bank's foreign reserves rose in December for a third consecutive month, a sign that higher oil prices may be easing pressure on the government's finances, official data showed. The state budget deficit this year is projected at 195 billion riyals.
Saudi Telecom also beat estimates with a rise of fourth-quarter net profit to 2.65 billion riyals from 2.08 billion riyals; its shares climbed 2.5 percent. Some analysts also question the extent of change if those who were held at the Ritz were allowed to return to their normal positions without clarity on whether they were found guilty or innocent.
"Saudi Arabia is still a big market in terms of fundraising and investing", Hazem Ben-Gacem, head of the Bahrain-based firm's European private equity business, said on the sidelines of the World Economic Forum in Davos. "The campaign against corruption won't stop".