6:48 AM PT -- Officials tell TMZ Sports ... Williams was initially pulled over for going 80 in a 50 on the Crescent City Connection Bridge.

During the stop, cops suspected he was intoxicated and tried to administer a breath test but Williams refused ... so he was arrested.

We're told he was booked for driving while intoxicated, speeding, improper lane usage and failure to use a turn signal.

A bad week just got worse for New Orleans Saints cornerback P.J. Williams -- who was arrested early Wednesday morning when cops say he was driving drunk in the Big Easy.

The 25-year-old -- a key player on the Saints defense -- was booked for drunk driving and careless driving at 1:10 AM, according to The Advocate.

After posing for a mug shot, Williams was released roughly 3 hours after his arrest. We're working on the details.

It's not the first time Williams has been arrested for drunk driving -- he was popped for DUI in Florida back in 2015 but the case was thrown out because police dash cam video failed to capture key moments from that arrest.

Williams was a stud back in college where he helped Florida State win the national championship playing with Jameis Winston back in 2013.

He later entered the NFL Draft in 2015 where he was selected by the Saints in the 3rd round.

Since turning pro, he's been a pretty solid player -- even picking off Kirk Cousins for a Pick 6 in the Week 8 battle this season against the Minnesota Vikings.

Williams played in 15 games in 2018 for the Saints -- posting 53 tackles, 1 interception and 1 sack.

He started in the NFC championship game against the L.A. Rams last weekend -- and had 8 tackles and broke up 1 pass in the 26 to 23 loss.