The former couple had apparently had a trial separation and have decided to move forward.
He made the announcement on Twitter.
The two have four children and have been together for 25 years.
Jeff Bezos was ranked the richest man in the world in 2018 by Forbes, which reports he is now worth more than $136 billion.
According to her author page on Amazon, MacKenzie Bezos studied creative writing at Princeton University and worked as a research assistant to author Toni Morrison. She also founded Bystander Revolution, an organization dedicated to combating bullying that counts Monica Lewinsky and actress Lily Collins as ambassadors.
MacKenzie Bezos is the author of two books, one of which won an American Book Award.
ABC News contributed to this report.