Denis Bambrick Cashman (March 1843 – 8 January 1897) was an Irish political prisoner and diarist who was transported to colonial Western Australia due to Fenianism and wrote of his experiences in a diary.

On 12 January 1867, Cashman was arrested (the same day his third child was born) and was brought to trial on 19 February 1867 where he pleaded guilty to treason, he was sentenced to seven years penal servitude.

In late October 1869, he and 14 other Fenians boarded the ship Baringa and sailed from Sydney, Australia to San Francisco, California.

He took the Central Pacific Railroad out of California and headed to Boston to meet up with his wife Catherine, his son William, and his good friend and fellow Fenian John Boyle O'Reilly.

[7] His diary was donated to East Carolina University where Professor of English Charles Sullivan III edited it and in this form it was published in 2003.