There are a few people who could lay claim to the title of largest pen collection. However, the most likely candidate is probably Dr. Sreekumar Achary, an Indian oncologist who has amassed over 4,000 pens.
Achary's collection began relatively modestly, with just a few fountain pens that he received as gifts. However, it quickly grew into something much larger, fueled by Achary's passion for writing and his love of collecting. Today, his collection includes pens from all over the world, including some very rare and valuable pieces.
While Achary may have the largest known pen collection, there are probably other people out there with even more extensive collections. After all, there are millions of passionate pen collectors in the world and it's hard to say definitively who has the biggest collection.