Google has acquired the engineering company that developed Cheetah, the world's fastest-running robot and other animal-based mobile research machines.
Boston Dynamics, which contracts for the US military, is the eighth robotics company snapped up by Google this year.
Both the price and size of the project, which is led by former Android boss Andy Rubin, are being kept under wraps.
However, analysts say the purchases signal a rising interest in robotics use by consumer internet companies.
Online shopping portal Amazon, for example, recently announced plans to deploy a fleet of delivery drones.
In a statement posted on the Google Plus service, Chief Executive Larry Page said:
"I am excited about Andy Rubin's next project. His last big bet, Android, started off as a crazy idea that ended up putting a supercomputer in hundreds of millions of pockets. It is still very early days for this, but I can't wait to see the progress."
Boston Dynamics, which does not sell robots commercially, was founded in 1992 by a former professor from the Massachusetts Institute of Technology.
It consulted for Japanese electronics giant Sony on consumer applications such as Aibo, a robot dog.
But it mostly develops mobile and off-road robotics technology, funded by the Pentagon's Defense Advanced Research Projects Agency, or Darpa.
Google has said it would honour the existing military contracts with Darpa.
Boston Dynamics' videos of its walking robots have garnered millions of views online.
One of them, called BigDog, is remarkably agile for a machine and is able to move over rough terrain such as snow and ice.
Another, of a four-legged robot named WildCat, shows the noisy machine galloping down a car park at high speed and pivoting quickly on the spot.