Ledecky has broken 14 world records and won six Olympic medals, but the 21-year-old didn't turn professional until after the NCAA collegiate championships in March.
California swimwear manufacturer TYR said in a statement on Friday that their deal with Ledecky "represents the most lucrative partnership in the history of the swim industry," although no terms were revealed.
In Friday's Pro Swim meeting sponsored by TYR, Ledecky won the 200m free in 1 minute, 54.56 seconds.
Melanie Margalis was a distant second in 1:57.99.
"That's exactly where I was hoping to be," Ledecky said. "I felt like I could go a 1:54 tonight, after going a 55 this morning. I just wanted to put together a really great race and make some adjustments off of this morning's swim.
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