Thomas Brittain Vacher (1805–1880) was a British lithographer, legal stationer, and printer.
He founded Vacher's Parliamentary Companion, a parliamentary reference work which continues to this day as Vachers Quarterly, published by Dods.
He went into business with his brother George; the third son Charles Vacher was known as an artist.
Thomas Brittain Vacher was himself an amateur artist.
His son, the architect Sydney Vacher, designed the elaborate pulpit in St Margaret's church, Westminster as a memorial to him.