Inga Simpson began her career as a professional writer for government before gaining a PhD in creative writing. In 2011, she took part in the Queensland Writers Centre Manuscript Development Program and, as a result, Hachette Australia published her first novel, Mr Wigg, in 2013. Nest, Inga's second novel, was published in 2014 and was longlisted for the Miles Franklin Literary Award and the Stella Prize and shortlisted for the ALS Gold Medal. Inga's third novel, the acclaimed Where the Trees Were, was published in 2016.

Inga was awarded the final Eric Rolls Prize for her nature writing and has obtained a second PhD, exploring the history of Australian nature writers. Inga's account of her love of Australian nature and life with trees, Understory, was published in 2017. Her first book for children, The Book of Australian Trees, illustrated by Alicia Rogerson, was published in 2021. The Last Woman in the World, her critically acclaimed environmental thriller, was published in 2021 and shortlisted for the 2022 Fiction Indie Book Award. Her bestselling and critically acclaimed 2022 novel Willowman was shortlisted for the BookPeople Adult Fiction Book of the Year 2023 and in 2024 was selected by Australia's leading booksellers in BookPeople's 100 Must-Read Australian Novels.

Inga lives on the New South Wales south coast among trees.