Williams had bounced back from a 2-0 deficit to lead Murphy 5-4 before the evening session.
He made breaks of 73 and 70 to help himself to three consecutive frames and the 3-2 lead, before notching his first century of the week with a 143 to take a 4-3 advantage.
But Murphy had begun the encounter with a display of some fine long-range cueing, and edged back in front, winning three out of four games at the start of the evening.
Selby's final-frame 98 sinks Hawkins in decider
Williams stayed in touch, and levelled the score at nine frames apiece with a century break - forcing a decider in which Murphy led from the front, and he wrapped up his 10-9 victory after a break of 69, finishing with a well-taken long red.
This was Murphy's third consecutive final this season - and the first he had won since 2017's Gibraltar Open.