In March the entire board of directors at Southern Health NHS Foundation Trust resigned after a review of its services.
The trust came under fire after Connor Sparrowhawk drowned at its Slade House facility in Oxford and boss Katrina Percy resigned in October.
Lynne Hunt will now take over as chairwoman of the trust on 3 July.
Previous interim chairman Tim Smart stood down after he was criticised for creating a new job for Ms Percy.
The trust is now being prosecuted by the Health and Safety Executive over Connor's death in 2014.
Ms Hunt was previously vice-chair at Dorset Healthcare NHS Foundation Trust and was described as having "a track record of almost 40 years public service".
She said: "With this new leadership and a board of newly appointed non-executive directors we can influence and develop a culture of change and improvement."
Southern Health provides mental health services to patients across Hampshire, Dorset, and Oxfordshire.
July 2013 - Connor Sparrowhawk, 18, drowns after an epileptic seizure at Oxford unit Slade House. An inquest later rules neglect contributed to his death
11 December 2015 - The BBC reveals details of a leaked Mazars report which highlights a "failure of leadership". Health Secretary Jeremy Hunt says he is "profoundly shocked"
17 December 2015 - The report is officially published and shows out of 722 unexpected deaths over four years, only 272 were properly investigated
6 April 2016 - The Care Quality Commission (CQC) issues a warning notice to significantly improve protection for mental health patients
29 April 2016 - A full CQC inspection report is published which says the trust is continuing to put patients at risk
30 June 2016 - Following a review of the management team competencies, it is announced that Katrina Percy is to keep her job
29 July 2016 - The BBC reveals the trust paid millions of pounds in contracts to companies owned by previous associates of Ms Percy
30 August 2016 - Ms Percy announces she is standing down as chief executive, but is staying on in an advisory role
19 September 2016 - Interim chairman Tim Smart resigns after admitting he created a job for Ms Percy
7 October 2016 - Ms Percy resigns completely from the trust
13 December 2016 - A CQC report, the culmination of a one-year inquiry, says investigations into patient deaths are inadequate
16 March 2017 - All the non-executive directors resign from trust
An NHS trust criticised for failing to properly investigate hundreds of deaths has appointed a new chairwoman.