Theresa May said the appointment of Health Minister Jackie Doyle-Price to the new role will help tackle the stigma surrounding suicide.
While suicide rates are falling, 4,500 people take their own lives every year.
The appointment comes as ministers and officials from more than 50 countries assemble in London for the summit.
Wednesday’s meeting – hosted by Health Secretary Matt Hancock and attended by the Duke and Duchess of Cambridge – coincides with World Mental Health Day.
The government has also promised more support in schools, bringing in new mental health support teams and offering help in measuring students’ health, including their mental wellbeing.
Ms May said: “We can end the stigma that has forced too many to suffer in silence and prevent the tragedy of suicide taking too many lives.”
Mrs Doyle-Price, who has been an MP since 2010, will now become the minister for mental health, inequalities and suicide prevention.
As health is devolved separately to the UK’s four nations, her role will include making sure each local area in England has effective plans to stop unnecessary deaths and to look into how technology could help identify those at risk.
Manchester University’s Prof Louis Appleby, one of the country’s leading experts on suicide, said having a minister for suicide prevention would “open doors” and make it easier to have conversations about the role such things as benefits and online gambling have in suicidal people’s lives.
Health Secretary Matt Hancock said the appointment would also help with getting support for mental illness on a par with services for physical health.
“There is a long road to travel to get there. This is not something you solve overnight,” he said.