Recently, someone made one of the biggest transactions in Bitcoin history: 94,504 Bitcoins. At the then-current Bitcoin price of around $10,600, this transaction was worth almost $1 billion. It's now worth around $967 million.
Bitcoin's shared transaction ledger is open, but addresses are anonymous by default. As a result, we know that the transaction occurred, but we don't know who made it or why. One analysis indicated that at least a third of the money comes from Huobi Global, a cryptocurrency exchange based in Singapore. So the transaction could reflect big withdrawals from a Huobi customer—or it could mean Huobi itself was merging some of its deposits.
This isn't the largest transaction in Bitcoin terms. In 2013, for example, someone moved 194,993 Bitcoins in a single transaction. But Bitcoins were less valuable back then, so the transaction was only valued at around $150 million.
An even more considerable 2011 transaction moved 550,000 Bitcoins. But with Bitcoins only worth around $3 at the time, this represented around $1.5 million at the time. However, I can't find any previous examples of Bitcoin transactions where the dollar value surpassed $1 billion. Whoever launched the $1 billion transfer, paid a transaction fee of 0.065 Bitcoins—around $690 at the time of the transaction.