Carrie Lam has become the first woman to hold Hong Kong’s top job.
The 59-year-old had the backing of the Chinese government in Beijing and was widely expected to win.
Hong Kong has a degree of autonomy from Beijing but protests have been growing over Chinese interference.
Hong Kong’s chief executive is not chosen by public vote but by a 1,200-strong committee dominated by pro-Beijing electors.
Pro-democracy groups held protests outside the election venue, calling the process a sham.
In her acceptance speech, Carrie Lam said her first priority during her five-year term would be to reduce social tensions.
She welcomed and encouraged a spectrum of voices and vowed to “tap the forces of our young people”: “They are often at the forefront of society, pulling and pushing us as a whole to make progress.”
Carrie Lam also promised to uphold Hong Kong’s “core values” such as “inclusiveness, freedoms of the press and of speech, respect for human rights” and the rule of law.
Her main rival, former finance chief John Tsang, was the public’s favorite, according to opinion polls.
The third candidate, and the most liberal, was retired judge Woo Kwok-hing.
Carrie Lam garnered 777 votes to John Tsang’s 365. Woo Kwok-hing received 21.
Calls for fully free elections have failed, despite intense demonstrations, known as the “umbrella protests”, in 2014.
Hong Kong’s Election Committee picked Carrie Lam to succeed current leader CY Leung, who will step down in July. She was formerly his deputy.
Carrie Lam, a long-time civil servant, is nicknamed the nanny because of her background running numerous government projects.
During the 2014 protests, which were spearheaded by young people, Carrie Lam took the unpopular stance of defending Beijing’s concessions for political reform.
This allowed Hong Kong people to choose their leader but only from pre-approved candidates.
Pro-democracy activist Joshua Wong, who was among those protesting and was a lead figure in the umbrella movement, has called the electoral process “a selection rather than an election”.
When the result was announced, he tweeted that Carrie Lam had been elected with “only 777 votes”.
On Facebook, an online protest was launched called No Election in Hong Kong Now, which showed a video montage of regular citizens going about their business as the election took place to highlight how they were not entitled to participate.
CY Leung has proved unpopular with large swathes of Hong Kong residents who consider him too tightly aligned to Beijing.
At the end of the 2016, CY Leung made the unexpected announcement that he would not run again, citing family reasons.
Hong Kong is governed under the principle of “one country, two systems”, under which China has agreed to give the region semi-autonomous status since its 1997 handover from Britain.
The Election Committee includes 70 members of the territory’s legislature, the Legislative Council – half of whom are directly elected.
However, most of the Election Committee is chosen by business, professional or special interest groups.
Critics say entities that lean towards Beijing are given disproportionately large representation.
In 2016, pro-democracy activists secured 325 seats on the committee – the highest number ever, but not enough seats to determine the next chief executive.