Prefix with marathon for a race over 26.2 miles NYT crossword clue

The answer to the clue “Prefix with marathon for a race over 26.2 miles” is ULTRA.

This clue is looking for a prefix that, when combined with “marathon,” refers to a race longer than the standard 26.2 miles. “Ultra” is commonly used to describe endurance races that exceed the traditional marathon distance, such as ultramarathons, which can range from 50 kilometers to 100 miles or more. The clue relies on recognizing this specific terminology, making ULTRA the correct and precise answer.