It is the first leadership vote since mass "Umbrella Movement" rallies calling for fully free elections in 2014 failed to win reform and comes after a turbulent term under current chief executive Leung Chun-ying.
Leung is seen by opponents as a Beijing puppet and will step down in July after five years in charge.
Hong Kong is semi-autonomous and has been governed under a "one country, two systems" deal since it was handed back to China by Britain in 1997.
Around three quarters of the 1,194 members of the election committee were from the mainland camp.
According to media counts, Lam won comprehensively with more than 700 votes against less than 400 for her more moderate establishment rival John Tsang.
Frustration at what activists see as China's increasing influence and a lack of promised political reform has sparked calls for self-determination for Hong Kong, or even a complete split from China.
Lam was widely seen as Beijing's pick for the job throughout the race and will become Hong Kong's first ever woman chief executive.
That plan said the public could choose the city leader in 2017, but insisted candidates must be vetted first.
It was eventually voted down in parliament by pro-democracy lawmakers and reforms have been shelved ever since.
Hundreds of protesters including leading pro-democracy activist Joshua Wong gathered near the harbour-front voting venue.
They chanted: "Oppose central authority appointment, we choose our own government!"
Protesters were held back by police as some tried to push through barriers.
Nearby, pro-China supporters played marching music surrounded by national and city flags.
"It is still a selection from the Beijing government," Law told AFP.
Disclaimer: No Business Standard Journalist was involved in creation of this content
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
