The 30-year-old was charged with eight counts of murder and 10 counts of attempted murder between June 2015 and June 2016 on Wednesday evening, police said.
Letby, from Hereford, will to appear at Warrington Magistrates’ Court on Thursday to face the charges.
Chester Police said in a statement on Wednesday: “The Crown Prosecution Service has authorised Cheshire Police to charge a healthcare professional with murder in connection with an ongoing investigation into a number of baby deaths at the Countess of Chester Hospital.
“Lucy Letby, of Arran Avenue, Hereford, is facing eight charges of murder and 10 charges of attempted murder. The charges relate to the period of June 2015 to June 2016.
“The 30-year-old was rearrested on Tuesday, 10 November, and has since subsequently been charged.
“She has been held in custody and is due to appear at Warrington Magistrates’s Court on Thursday, 12 November.”
On Tuesday, police said parents of all the babies involved were being kept fully updated on developments and were supported by officers.
Ms Letby was arrested by police in 2018 and 2019 but was bailed pending further inquiries.