Trump decided on the nomination Tuesday, the White House said. Abizaid must be approved by the Senate.
Abizaid is a retired four-star Army general and West Point and Harvard University graduate. He's a Stanford University fellow lecturer and heads the security consulting firm JPA Partners in Nevada.
He served as head of U.S. Central Command from 2003 to 2007, the longest tenure of anyone in that position. In the post, he oversaw the U.S. military's involvement in Iraq and was the top U.S. commander in the Middle East.
Relations between the United States and Saudi Arabia have been uneasy recently, following the death of dissident journalist Jamal Khashoggi. Investigators believe a Saudi hit team killed Khashoggi last month at a Saudi consulate in Turkey.
Through the ordeal, Trump has repeatedly said he values the U.S.-Saudi partnership. Saudi Arabia agreed to purchase billions of dollars in arms from the United States last year.
Trump, while calling for a full investigation of Khashoggi's death, has said any diplomatic punishment by the United States will not include interrupting the arms sales.
The ambassador's position has been vacant since Joseph Westphal, a Pentagon official and appointee of former President Barack Obama, departed when Trump took office in January 2017.