That would be...the University of Michigan, with 68. The Ohio State "University" has produced, by contrast, 62 professional athletes, second-most among American universities.
Here's the top ten:
1. University of Michigan
2. The Ohio State "University"
3. University of Miami
4. University of California at Los Angeles (UCLA)
5. (tie) Florida State "University"
5. (tie) University of Notre Dame
7. (tie) University of North Carolina
7. (tie) Louisiana State "University"
7. (tie) University of Florida
10. University of Tennessee
Michigan is also the number one school for producing NHL players, notably Dallas Stars and Canadian Olympic team goaltender Marty Turco.