"It's an amazing feeling to be in your first final. It's what we work hard for," said Ruud. "But even though it's been an amazing week, I'm hungry to win the last match."
The 22-year-old Garin defeated Sam Querrey of the US 7-6 (7/2), 6-2 in the other semi-final on Saturday.
Ruud had to battle back from an 2-5 deficit in the opening set to dispatch the Colombian Galan.
Galan finished his rain-delayed quarter-final earlier in the day over seventh seed Jordan Thompson of Australia, winning 6-1, 4-6, 6-4.
Ruud has been impressive on clay this season. He reached the quarter-finals in February at the Rio Open and then advanced to the semi-finals at the Brazil Open.
Garin is also looking for his first ATP title after advancing to his second clay court final of the season.
Garin won their only previous career meeting last month.
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