The WTA International hard-court decider in Quebec City will feature 66 years of experience, with Croatian veteran Lucic-Baroni, 32, taking on seven-time major winner and stalwart Williams, 34.
Lucic-Baroni is into her first WTA Tour final since 1998, after downing German fifth seed Julia Goerges 6-4 5-7 6-2 in two hours 23 minutes.
The Dortmund-born Lucic-Baroni stormed into the US Open fourth round in September, and has carried her good form into the tournament in Canada - and is eyeing her first title since defending her Croatian Bol Ladies Open (now defunct) crown in 1998.
Since then, she has lost twice to Williams in hard-court matches 11 years apart - one of those results was a double-bagel victory at the US Open in 2002.
The American beat compatriot and fourth seed Shelby Rogers 6-3 6-3 in one hour 21 minutes, to enter her 75th career tour final.
Williams is aiming to add to her 45 titles.