The price fell to $5,947.40 (£4,256.44) on Tuesday, according to a price index run by news website Coindesk.
Bitcoin reached its peak in November, when it hit $19,000, and then began to fall steadily from mid-December.
The latest fall comes a day after several major US and UK banks banned customers from using credit cards to purchase the digital currency.
Tightening legislation in several countries appears to have shaken confidence in crypto-currencies.
As of Tuesday:
The price of Ethereum, which at its height on 9 January was $1,255.89, is now $574.42
Bitcoin Cash, which hit a peak $4,091.70 on 20 December 2017, has slipped to $766.03
Litecoin, which reached $366.01 on 19 December 2017, has dropped to $106.94
Tightening legislation
Chinese state media is reporting that China will soon take steps to prevent investors from accessing foreign virtual currency exchanges, although it is not clear how the government intends to achieve this.
China and South Korea have already banned digital currencies, while Japan and Australia have taken steps to tighten Bitcoin regulations.