Peter Foster who was jailed last month after admitting murdering Heather Cooper has been found hanged in his prison cell.
It is understood Foster was subject to suicide-prevention measures at Lewes jail.
A spokesman for the Prison Service said: “Prison staff tried to resuscitate him and paramedics were called but he was pronounced dead at 03.25.
“As with all deaths in custody, the independent Prisons and Probation Ombudsman will conduct an investigation.”
33 year old Heather, mother to their two young children was found dead in woodland at Lurgashall last October.
Foster stabbed Heather, a detective constable with Surrey Police while she was on maternity leave following the birth of their second child.