With the rest of the All England Club in darkness at the end of a long day, Townsend and Siniakova shone under the illuminated Centre Court roof to win 7-6(5) 7-6(1) in what was only their 10th match playing together.
Townsend had lost in the US Open doubles final in 2022 and last year's French Open doubles final, but made it third time lucky alongside Siniakova who now has nine doubles Slams.
Chicago-born Townsend, who became a mother in 2021, was overcome with emotion after a double fault from their opponents ended a tight contest.
"I just have to say I'm so glad that I could team up with Katerina," Townsend said on court.
"I remember in my first Grand Slam final (the 2022 US Open) she kicked my butt so it was great to be on the same side of the net this time. It's been an amazing couple of weeks and it means a lot to get across the finishing line."
Routliffe, who alongside Dabrowski, won the US Open doubles title last year, will take some consolation in reaching the number-one spot in the women's doubles rankings.
"This was my first Wimbledon final but hopefully not my last," Routliffe said on court.
"There is something about Wimbledon that makes every match so much more emotional."
Siniakova won her first two Wimbledon doubles crowns with Barbora Krejcikova who earlier on Centre Court beat Jasmine Paolini to claim the singles title.
"I'm so proud of Barbora and I'm so happy that we could do it as well," Siniakova said.
