The Lions trailed by three after the first quarter but led 49-45 at the interval thanks to three Tarik Phillip three-pointers.
Phoenix deep-threat Skyler White kept his side in touch from beyond the arc and Cheshire came back to take the lead with a 12-0 run late in the third quarter after a succession of defensive stops, some clinical fast-break finishing and a series of free throws.
Lions point guard Jordan Taylor came off the bench to cut the gap to 67-61 as time expired in the third quarter and almost single-handedly turned an 11-point deficit into a three-point advantage early in the fourth.
However, Rideau hauled Chester back into an eight-point lead as the Lions went scoreless for nearly four minutes in the final period and the Phoenix lead became unassailable after a White effort from distance with just over two minutes remaining.
Then named the Jets, the Chester franchise won four straight BBL Trophy titles from 2001-04 and are now only one behind Newcastle for most Trophy wins.
Rideau, who was named MVP in the final, told Sky Sports: “Going back to September everybody doubted us – some had us down at eight or nine. I know, I kept it.
“I knew what we had got, I believe in my team. We have got a great group of fans, we love them. We are not underdogs, we are top dogs.”
Ben Thomas, Phoenix head coach, added: “After last year, I am so happy. I am so happy we can win this for our fans.
“It feels so good. We knew we let that one slip (in 2023). Especially in that second half we took it to them and left it all out there.”
Lions captain Taylor added: “They made their shots and played defence. They came prepared. We only had 30-some points in the second half – hats off to them.”
The Lions had booked their place in the final on Saturday night as they came from 15 points behind to see off defending champions Caledonia Gladiators 85-75. Josh Sharma led their comeback, scoring 19 points off the bench, and Gabriel Olaseni collected 18 points and 15 rebounds in less than 18 minutes on court.
In the other semi-final, Rideau’s lay-up with six seconds remaining ensured Cheshire pipped Leicester Riders 92-91, having seen a 12-point lead clawed back late-on.
Aaryn Rai posted 27 points with 11 rebounds, while Rideau’s game winner took him to 15 points to add his 13 assists.
