This was the fifth such "selection" in the 20 years since Hong Kong was returned to Chinese sovereignty in 1997 - and perhaps the most contentious.
Under a political compromise known as "One country, two systems," the territory was promised a "high degree of autonomy," including the right to elect their leader by 2017.
Many Hong Kong people believe Beijing broke its word. Instead of getting more autonomous and democratic, critics argue, Hong Kong is increasingly being strong-armed by cadres in Beijing.
"We have been waiting for 20 years now and the electoral law is still not fair or democratic," said Martin Lee, a veteran pro-democracy campaigner.
"Beijing has tried to rule Hong Kong by controlling us."
"One country, two systems" has always been an unhappy compromise, one that pits the People's Republic of China's intransigent Communist Party against Hong Kong's scrappy pan-democratic camp.
With an electoral system stacked in favour of the central government, the pro-democratic movement has used mass protests against the government, blocking an unpopular state security law in 2003 and, more recently, thwarting Beijing's plans for "patriotic education" in Hong Kong.
In August 2014, Beijing issued a white paper on the territory's future that many Hong Kong people saw as a step too far. The 14,500-word document stressed that the central government has "comprehensive jurisdiction" over the territory.
"The high degree of autonomy of the HKSAR (Hong Kong Special Administrative Region) is not full autonomy, nor a decentralised power," it read. "It is the power to run local affairs as authorised by the central leadership."
In response to the 2014 paper, student leaders such as Joshua Wong led tens of thousands into the streets, occupying the heart of the city. When police fired pepper spray at the crowd, they used umbrellas to shield their faces - and the Umbrella Movement was born.
Months of protests did not secure any concession from Beijing, which doubled down instead.
"In the original 'One country, two systems,' the message was 'Hong Kong people, put your hearts at ease,'" says Michael Davis, a former constitutional expert at Hong Kong University, "Since 2014, the message has been, 'Beijing is the boss.'"
The central Government's hardline stance continues to divide the city. In 2015, when Beijing put forward a election blueprint that would see the chief executive elected by popular vote - but from a list of vetted candidates - the pro-democratic camp decried the plan.
Frustration over electoral reform and other issues has fuelled a small but vocal group of Hong Kong independence activists.
Last November, Beijing intervened in a Hong Kong court case to block two politicians from taking seats in the city's legislature. Both had pledged allegiance to the "Hong Kong nation," not the People's Republic of China, while taking their oaths of office.
Though the reach of the independence movement remains limited, the incident served as "a useful pretext for Beijing to justify curtail freedom of election and expression," said Willy Lam of the Chinese University of Hong Kong. "There's a real fear that Beijing will use the pretext of a separatist movement to crack down."
Beijing is becoming bolder about interfering in Hong Kong affairs, experts said.
In January, a China-born tycoon was wheeled out of a luxury Hong Kong hotel in a wheelchair and then turned up in police custody across the border - an incident that reminded many of the 2016 abduction and detention of five Hong Kong booksellers.
Lam's win will do little to ease concern about Beijing's influence. Given limited popular support, her government may struggle to stop violations of Hong Kong's mini constitution or speak up against Beijing, experts said.
"There is substantial apprehension that she will follow the overall policies of unpopular politics of (predecessor) C.Y. Leung, who is seen as too loyal in carrying out Xi Jinping's draconian measures," said Lam of the Chinese University of Hong Kong.
Veteran democracy activists stressed that it's not really about who won the chief executive race.
"Whoever is chief executive, the policy will continue, because at this point they just execute the policy of the central government - increase government control of political and social life, of the economy, and to promote integration between the mainland and Hong Kong," said Ho Fung Hung, an associate professor at Johns Hopkins University
"It's not a matter of whether he will win or she will win," agreed Martin Lee. "Unless Beijing's policy changes for the better, changing the chief executive alone is not that useful, because if Beijing continues to dictate to them how to rule, there is no change."
