The Baudelaire Fortune is a large, unspecified amount of money that was left behind by Beatrice and Bertrand to their children. Count Olaf was vying for it throughout A Series of Unfortunate Events by getting his hands on the Baudelaire orphans in any way he can and would have been given to them when Violet comes of age.
If The Puzzling Puzzles is canon to the main series, the fortune is said to be about 130 shoeboxes full of golf ball-sized diamonds. It is unclear if this simply refers to the value, or if the description was literal.
A certain reader of the book series did the math, and equated the overall fortune to be worth $474,250,944,375 (four-hundred seventy-four billion, two-hundred-fifty million, nine-hundred forty-four thousand, three-hundred seventy-five dollars). In other currency, this would equate to €426,408,000,000 (four-hundred twenty-six billion, four hundred and eight million euros) or £363,182,000,000 (three-hundred sixty-three billion, one-hundred and eighty-two million pounds). This would make the Baudelaire family one of the wealthiest to exist in the world at the time the series took place.
How and when Beatrice and Bertrand Baudelaire obtained or built the family fortune is unknown. Considering it is referred to as the "Baudelaire Fortune", it is likely that the money belonged mainly to the parent that originally had the surname Baudelaire. (Presumably, Beatrice, considering she was referred to as B.B. before marriage.)
Due to their parents' specific wishes in their will, their children are not allowed to spend even one cent until at least one of them turns 18 years old; in this case, Violet Baudelaire would be eligible to use it the soonest since she is the eldest child, and would hypothetically inherit it within four years post-The Bad Beginning. Furthermore, neither Arthur Poe nor Mulctuary Money Management as a whole refused to allow Violet nor her younger siblings to outright claim it. The fortune was also not to be used for or by any of the Baudelaire guardians.  Thankfully, this prevented Count Olaf from accessing the fortune himself, forcing him to attempt to take advantage of a variety of legal loopholes to bypass this restriction.
The fortune is Count Olaf's main incentive for tormenting the Baudelaires in the first place, but it has been debated that the primary reason for his involvement in the Baudelaires' lives could be something else that not been made entirely certain, such as his negative relationship with the Baudelaire parents. He has made it clear that after obtaining the fortune, he will not hesitate to kill the children.
It is ironic that the Baudelaire fortune was intended to improve the children's lives when it actually became a burden for them due to Count Olaf's constant pursuit of them. If the Baudelaires were to somehow never inherit the fortune at all, then Count Olaf may have left them alone and none of the series of unfortunate events would have happened. The Baudelaire children also occasionally live in poverty, as they couldn't afford a basic bed in The Bad Beginning, and are at the mercy of the world as fugitives as of the end of The Vile Village, although it could be argued they were at the mercy of the world before then.
By the end of the series, it's unclear if either of the Baudelaire orphans ever inherited the fortune years later, similar to how it's also a mystery if they all survived. In The End, Violet stated, "None of us may ever see a penny of that money", which meant she had accepted this possibility.
- While living with Count Olaf, Klaus Baudelaire says that if he could use the fortune now instead of in years, he would buy a castle and live in it, with armed guards patrolling the outside to keep out Count Olaf and his troupe. Violet Baudelaire would like an inventing studio, Klaus a library, and Sunny things to bite.
- Violet later mentions that if she obtained the fortune, she would like to build an inventing studio for herself, potentially over Lake Lachrymose where Aunt Josephine's house used to be so she could be remembered. Klaus mentions he would build a public library, and buy back Uncle Monty's reptile collection, and take care of all the reptiles. Sunny mentions she would be a dentist.
- Olaf mentions that the first thing he'd buy is a shiny new car named after himself.
- Esmé Squalor mentions she wants the fortune because money is "in".
- One popular fan theory is that the Baudelaire fortune is the remains of Count Olaf's fortune, stolen by the Baudelaire parents and Kit Snicket after murdering his parents, which would explain Olaf's personal vendetta against the Baudelaire family, why he seems to live in poverty despite being royalty, and the motive behind the assassination of his parents.
- Another popular theory is that Mrs. Bass stole the Baudelaire fortune sometime before The Penultimate Peril; it is known that she was arrested for bank robbery, and that the crime was committed during or after Vice Principal Nero's letter in Lemony Snicket: The Unauthorized Autobiography and before the burning of the Hotel Denouement. It is also noted that Arthur Poe was sent to the hotel after Bass to investigate a bank robbery, and it would make sense if he, as the executor of the Baudelaire parents' estate, was the one to investigate its theft.
- If the banking system in the universe of A Series of Unfortunate Events is similar to that of reality, this may be unlikely, as banks tend to not keep all their cash in the building, instead keeping only enough to meet their anticipated transaction needs and depositing the rest in the Federal Reserve Bank. So if Mrs. Bass stole the Baudelaire fortune, it is unlikely she stole all of it. However, the banking system of the Snicket universe may work differently.
- The theory is also likely non-canon in the Netflix series, as Bass steals the money in between "The Austere Academy: Part Two" and "The Slippery Slope: Part One," with the implication that she planned to take part in the robbery before the Baudelaires even attended Prufrock Preparatory School,, and the fact she was caught before the Hotel Denouement Fire and Poe attended the trial at the request of J.S..
- Baudelaire Fortune Math.
- PROSE: The Beatrice Letters
- PROSE: The Bad Beginning
- PROSE: The Penultimate Peril
- PROSE: The Miserable Mill
- PROSE: The End
- PROSE: The Ersatz Elevator
- Full Theory - Why were Olaf's parents assassinated?
- TV: The Penultimate Peril: Part Two
- Full Theory - Did Mrs Bass steal the Baudelaire fortune?
- How much Money Can a Bank Hold?
- TV: The Austere Academy: Part One
- TV: The Austere Academy: Part Two
- TV: The Slippery Slope: Part One
- TV: The Penultimate Peril: Part One