The legendary author, born Samuel Clemens, would be 182 years old today.
To celebrate, here's a few reasons why he's still one of the greats.
Well perhaps not, but he did make one spooky prediction that came true.
Sure enough, he died of a heart attack in 1910 – the day after the comet returned.
In addition, when his younger brother, Henry, died in a steamboat accident in 1858, Twain claimed to have foreseen it in a dream a month earlier.
Due to a series of bad investments, Twain suffered financial setbacks later in life.
When the publishing firm he backed went bankrupt, Twain stepped in to ensure all creditors were fully paid – despite no legal obligation to do so.
Twain loved to travel and had many adventures from piloting a riverboat down the Mississippi to touring Europe and the Middle East.
In 1869, he wrote The Innocents Abroad, a compilation of letters he wrote while travelling.
Twain's father died when he was just 11, and he dropped out of school the following year to help support his family.
He became a printer's apprentice, while continuing his education in his free time – spending his evenings in public libraries.
Twain and his wife, Olivia, were married 34 years and had four children – three girls and a boy who died in infancy.
They were deeply in love and he often credited her with making him a better man.
Twain is best known for his two major works – The Adventures of Tom Sawyer and Adventures of Huckleberry Finn – but he produced a lot more than that.
Between his journalism, travel books and notes, Twain has a massive body of work and is frequently credited as being the father of American literature.
Twain was an ardent supporter of women's suffrage.
Samuel Clemens is best known as Mark Twain, but he used a lot of other pen names too – some of them showing his trademark wit and sense of humour.
Controversy remains over where Clemens got 'Mark Twain' from. Some literary historians claim Mark Twain was an actual person – a riverboat captain who also used it as an alias.
Others think Clemens took it because, in sailing jargon, 'Mark Twain' is a term used to describe whether water is deep enough for boat passage.