The City midfielder achieved the landmark when setting up Erling Haaland for the first of the Norwegian’s two goals at the St Mary’s Stadium.
With Jack Grealish and Julian Alvarez also on target it made for a fine afternoon’s work on the South Coast.
For De Bruyne it saw him hit the landmark in just 237 games.
Asked about the feat of reaching 100 Premier League assists in record time, De Bruyne said: “Of course I am proud.
“I saw it before the game. A lot of people were talking about it online.
“It is something you can’t really miss. I just tried to create as much as possible. I could have had two or three more. If they score I get the assist.
“I am known for my creativity, there aren’t many football players who have been there. Half of the side is mine and half of the side is the other.
“It is a proud moment but I have to go on.”
The Belgian’s achievement was thrown into further sharp focus by the fact he has achieved it 56 games quicker than Cesc Fabregas who held the previous record.
But for De Bruyne it was a case of seeking to try and produce his best for the team rather than individual plaudits.
“I don’t compare,” KDB added.
“Cesc is an unbelievable footballer player. I don’t compare myself to others. I just try and do the best I can do.
“People will talk about (being) quicker. Everything is different, you play different positions and teams.
“We score a lot of goals!”
It was also De Bruyne’s seventh assist for Haaland this season and took Haaland’s tally to 30 in the Premier League and 44 overall.
And the midfielder was full of praise for the Norwegian’s prowess and remarkable impact this season.
“He scores a lot of goals. It is insane,” De Bruyne added.
“He is there. If we create chances he is there. It is a good combination.
“He knows what I want to do and i know what he wants to do.”
