Brunt, 36, steps away from the game as England Women's third-leading Test wicket-taker with 51 wickets. She will continue to play ODI and IT20 cricket.
Brunt made her Test debut in 2004, and was part of a momentous moment for English cricket in just her third Test match - taking nine wickets across the match and scoring 52 to help Clare Connor's team retain the Women's Ashes after 42 years.
She retires having enjoyed the tenth-longest Test career in the history of the women's game.
Brunt said: "I feel like as an athlete there is never an obvious time to step away from doing the thing that you love.
"But over the past two years thoughts of retirement have surfaced more and more, so I’ve decided to make a smart decision rather than an emotional one. Test cricket is my absolute passion and to retire from this format was truly a heart-breaking choice to make, but it allows me to prioritise white-ball cricket."
"I know that I leave it in a great place, the bowlers coming through are ready and they’re just itching to be let loose! And with the South Africa game around the corner, I’m very much looking forward to watching them from the best seat in the house."
Jonathan Finch, Director of England Women's cricket, said: "Katherine’s passion and commitment was never more evident than when she played Test cricket for England and you only need to watch the last Ashes Test to see her desire, her heart and her undoubted ability with the red ball in hand.
"She has given everything for England Women in Test cricket and we are fully supportive of her decision to focus on white-ball cricket on the international stage. Katherine can leave the red ball behind knowing she is a true legend in that form of the game and that she has set standards that future generations can only aspire to."