Google’s ambitions and investments have increasingly broadened beyond its digital origins in Internet search and online advertising into the arena of physical objects: self-driving cars, Internet-connected eyeglasses, smart thermostats and a biotech venture to develop life-extending treatments.

Now Google is getting into the ultimate manifestation of the messy real world: cities.

The Silicon Valley giant is starting and funding an independent company dedicated to coming up with new technologies to improve urban life. The start-up, Sidewalk Labs, will be headed by Daniel L. Doctoroff, former deputy mayor of New York City for economic development and former chief executive of Bloomberg L.P. Mr. Doctoroff jointly conceived the idea for the company, which will be based in New York, with a team at Google, led by its chief executive, Larry Page.

The founders describe Sidewalk Labs as an “urban innovation company” that will pursue technologies to cut pollution, curb energy use, streamline transportation and reduce the cost of city living. To achieve that goal, Mr. Doctoroff said Sidewalk Labs planned to build technology itself, buy it and invest in partnerships.

“It’s going to evolve and we’re just starting up,” he said in an interview.

Neither Mr. Doctoroff nor Google would say how much Google intended to invest in Sidewalk Labs, but it could be sizable eventually. A model for Sidewalk Labs, they said, is Calico, a company backed by Google, established in 2013 and run by Arthur D. Levinson, a former Genentech chief executive. Last September, Calico and AbbVie, a pharmaceutical company, announced that they would build a research center in the San Francisco Bay Area for diseases that affect the elderly, like dementia, with an initial investment, split evenly, of $500 million.