Courville, the 1995 champion and '99 runner-up from Milford, Conn., beat John Pate in the morning quarterfinals and defending champion Tim Jackson in the semifinals in the afternoon.
Zahringer, the 2001 runner-up and a member at The Stanwich Club, moved into the final for the second straight year with wins over Austin Eaton and Jeff Wilson.
The finalists each live some 35 miles from the club. Zahringer is a nine-time Metropolitan Golf Association Player of the Year, while Courville has earned the Met honors four times.
The 49-year-old Zahringer, who is vying to become the oldest champion in the event's 22-year history, defeated Wilson, 5 and 4, in the semifinals after a 3 and 1 quarterfinal win over Eaton.
'It's something that's been on my radar screen for a number of years,' said Zahringer. 'I've always dreamed of doing well here. It's a tremendous sensation to have qualified and have gotten through five matches.'
Courville, meanwhile, will be making his third appearance in the final after dispatching Pate, 3 and 2, in the quarters and Jackson, 2-up, in the semifinals.
'Any time you get a chance to play for a national championship, it's a great honor,' said Courville. 'I'm going to go out and play my best and see what happens.'
The U.S. Mid-Amateur, for players 25 and older, is one of 13 national championships conducted annually by the United States Golf Association, 10 of which are strictly for amateurs.