Bill Gates is siding against Apple in saying the firm should help the US government to hack into a locked iPhone as part of an investigation into the San Bernardino shooting, which left 14 people dead.
Apple has resisted providing a piece of programming that would help the FBI access the phone.
Apple argues that governments, both in the US and overseas, are likely to use the program in other cases, undermining data privacy.
In an interview on Tuesday with the Financial Times, Microsoft founder Gates says "this is a specific case where the government is asking for access to information".
He likened it to the police getting records from a phone company.
The heads of many tech companies like Facebook, Twitter and Google have sided with Apple.
