1901 (MCMI) was a common year starting on Tuesday of the Gregorian calendar and a common year starting on Monday of the Julian calendar, the 1901st year of the Common Era (CE) and Anno Domini (AD) designations, the 901st year of the 2nd millennium, the 1st year of the 20th century, and the 2nd year of the 1900s decade. As of the start of 1901, the Gregorian calendar was 13 days ahead of the Julian calendar, which remained in localized use until 1923.

December 13 of this year is the beginning of signed 32-bit Unix time, and is scheduled to end in January 19, 2038.

1901 started with the unification of multiple British colonies in Australia on January 1 to form the Commonwealth of Australia after a referendum in 1900, Subsequently, the 1901 Australian election would see the first Australian prime minister, Edmund Barton. On the same day, Nigeria became a British protectorate.

Following this, the Victorian Era would come to an end after Queen Victoria died on January 22 after a reign of 63 years and 216 days, which was longer than those of any of her predecessors, Her son, Edward VII, succeeded her to the throne.

The date of Friday December 13 20:45:52 1901 is significant for modern computers because it is the earliest date representable with a signed 32-bit integer on systems that reference time in seconds since the Unix epoch. This corresponds to −2147483648 seconds from Thursday January 1 00:00:00 1970. Software that depends on this representation cannot represent an earlier date.

Similarly, many computer systems suffer from the year 2038 problem, when the positive number of seconds since 1970 exceeds 2147483647 (01111111 11111111 11111111 11111111 in binary) and, if represented as a signed 32-bit integer, wraps to −2147483648, representing Friday December 13 20:45:52 1901. In a way, the year 2038 problem for using signed 32-bit integers with January 1, 1970, as the zero date is as the year 2000 problem was for software using two-digit decimal integers with January 1, 1900, as the zero date.