It was the first international treble for the 27-year-old striker -- who joined Barcelona as a free agent this summer -- as the Dutch posted an emphatic victory for the second time in four days. The big win put them on 13 points from six games and vaulted them above Turkey at the head of the group.
Davy Klaassen scored in the opening minute to make a dream start for the home side, who had lost 4-2 to Turkey in Istanbul in March at the start of the qualifiers for the Qatar 2022 finals, before Depay added three more, including a penalty.
The result means Turkey slip from top to third in the group as they remain on 11 points with Norway moving second, behind the Dutch on goal difference, after beating Gibraltar 5-1 on Tuesday.
It was a night for dominance by the Dutch, who picked up where they left off after Saturday's 4-0 win over Montenegro to snatch the lead as Klaassen combined with Depay to score almost straight from the kick-off. An aggressive Dutch approach led to Klaassen then providing the assist for Depay's first goal in the 17th minute as they doubled the score, and it was 3-0 at halftime after Depay converted a 38th-minute penalty.
Leicester City defender Caglar Soyuncu was booked for a foul on Klaassen to concede the spot-kick, which was awarded after a VAR check. The Turkey defender was then sent off for a second caution on the stroke of halftime. From there, Depay completed his hat-trick with a diving header on the goal-line to touch home Steven Berghuis's cross in the 54th minute, before Til and Malen sealed the win with two more goals.
The one blemish came from a errant pass from goalkeeper Justin Bijlow that allowed Under to score for Turkey with the last kick of the game.
All in all, it was a triumphant night for veteran coach Louis van Gaal at the start of his third spell as coach. He had just days to prepare the team for their draw in Norway last Wednesday, but has since engineered two emphatic wins and a clear path to automatic qualification for the 2022 World Cup in Qatar.