The ICO said in a statement on Tuesday that it would be imposing the fine for infringements of the EU General Data Protection Regulation.
Marriott said last year that the breach, which affected its Starwood line of hotels, had exposed the data of 500 million guests to theft.
The hotel chain said it had become aware of the breach on 8 September 2019 and investigations had shown that data was being exfiltrated since 2014.
Information Commissioner Elizabeth Denham said: "The GDPR makes it clear that organisations must be accountable for the personal data they hold.
"This can include carrying out proper due diligence when making a corporate acquisition, and putting in place proper accountability measures to assess not only what personal data has been acquired, but also how it is protected.
“Personal data has a real value so organisations have a legal duty to ensure its security, just like they would do with any other asset.
"If that doesn’t happen, we will not hesitate to take strong action when necessary to protect the rights of the public.”
In a statement to the US Securities and Exchange Commission, Marriott International's president and chief executive Arne Sorenson said: "We are disappointed with this notice of intent from the ICO, which we will contest.
"Marriott has been co-operating with the ICO throughout its investigation into the incident, which involved a criminal attack against the Starwood guest reservation database.
“We deeply regret this incident happened. We take the privacy and security of guest information very seriously and continue to work hard to meet the standard of excellence that our guests expect from Marriott.”
This is the second fine for data breaches announced by the ICO on successive days. On Monday, it said British Airways would be fined £183.39 million (A$329.1 million) for a data breach that occurred in September 2018.