Chief Constable Ken Jones is quitting Sussex next year to become the full-time president of the Association of Chief Police Officers (Acpo).
Mr Jones, 53, will take up the three-year presidency in April at the end of the term of office of the current president, Chris Fox.
Mr Jones said: "I am very pleased to have been elected and, as president, I intend to positively develop national policing policy in ways which actively build on the local policing style which we have created here. I also intend to champion modernisation and much-needed change in ways which acknowledge our traditions, values and ethos."
Last autumn Mr Jones was beaten to the £225,000-a-year job of Metropolitan Police Commissioner by Sir Ian Blair.
He came under fire for applying for a London job at a time when he was encouraging lower-rank officers to stay in Sussex and not move to the capital where they can earn £6,000 more.
He was trying to counter a drain of experienced officers from Sussex.
Mr Jones said, if appointed commissioner, he would try and hire only London-based officers.
His new Acpo job is in the capital, in Victoria Street.
Peter Jones, chairman of Sussex Police Authority, said he was sorry to lose a "very fine" chief constable.
He said: "Under his leadership we have seen Sussex Police rise steadily in the national performance tables and the force has been a leader in the implementation of neighbourhood policing and the introduction of police community support officers."
In an internal message to his Sussex Police workforce, Mr Jones said: "In a few hectic years we have managed to restore Sussex to its rightful place. We are now a force to be reckoned with."
Mr Jones, whose income will increase by about £50,000 a year to £170,000, has been chief constable since 2001.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article