Sir Ara is chair of surgery at Imperial College London, where he is head of the division of surgery, oncology, reproductive biology and anaesthetics. His main clinical and academic interest is in minimally invasive therapy.
Sir Ara said his appointment 'signals the commitment of our new prime minister to value the leadership, experience and challenge of clinicians'.
Number 10 said he will work with health secretary Alan Johnson to improve.patient care, increase the convenience and accessibility of health services and build a new partnership with NHS staff and patients.
Sir Ara said his appointment was 'a great honour and a privilege'.
'I will be working closely with Alan Johnson to map out the next steps of the reform agenda that has achieved so much in the last 10 years. But we can do better,' he said.
'The prime minister has asked me to concentrate on how we can improve the quality of patient care, increase the convenience and accessibility of health services and build a new partnership with NHS staff and patients.
'My remit will be reliant on my experience as a clinician working in the NHS and my previous involvement in service redesign and improving access.'
Sir Ara.promised to be an advocate for NHS staff 'at the heart of government'.
'I approach this new role with humility but also with confidence in my knowledge of the needs of patients both now and in the future, together with an absolute determination to break down any barriers that prevent staff in the NHS from continuously meeting world-class standards of care for patients.'
NHS Confederation chief executive Dr Gill Morgan said Sir Ara had an excellent understanding of the political, managerial and clinical agendas, as well as being a first-rate surgeon.
'We are pleased that the new prime minister is bringing in new ministers with first-hand knowledge of the health service and clinical challenges.
'This is especially important as a major issue at present is re-engaging clinicians in the reform agenda.'