Here are some factors to consider:
* Piece Count: The highest piece count puzzle I could find was a 32,256 piece Ravensburger puzzle called "The World is a Book". However, there might be larger ones out there that aren't widely known.
* Surface Area: Some puzzles might have fewer pieces, but be larger in surface area. For example, a 10,000 piece puzzle with larger pieces could have a larger surface area than a 30,000 piece puzzle with tiny pieces.
* Custom Puzzles: You could technically commission a puzzle with any number of pieces, making it difficult to claim a definitive "largest."
So, there's no single answer to your question. It really depends on how you define "largest"!