The ISS Shenzhou was the Terran Empire counterpart of Georgiou's ship, formerly commanded by the mirror Michael Burnham, whose place the prime-universe Burnham took in order to steal imperial data.
The ISS Shenzhou appears in the Discovery episodes Despite Yourself, The Wolf Inside and Vaulting Ambition. In the mirror universe Burnham was its captain until she vanished, supposedly killed by Gabriel Lorca, and Danby Connor took command. The prime Burnham boards it, presenting Lorca as her prisoner, and has to kill Connor when he attacks her in a turbolift, to the applause of the bridge crew.
She finds a ship crewed by twisted versions of her dead colleagues, with Keyla Detmer as first officer and the Saru of that universe serving as a nameless slave.
From the Shenzhou she is ordered to wipe out a rebel base on Harlak, tries to warn its leaders, and is then summoned to the palace ship Charon by the emperor, Philippa Georgiou.