Which scientist formulated laws of motion for rigid bodies that extend Newton's laws?

Leonhard Euler formulated laws of motion for rigid bodies that extend Newton’s laws. Euler’s equations add the rotational dynamics needed to describe bodies with size, shape, and distributed mass.

Newton’s laws are naturally introduced for point particles, where the key quantities are net force, linear momentum, and acceleration. A rigid body can also translate, but it may rotate at the same time. Euler’s first law relates the net external force to the change in linear momentum; his second law relates external torque to the change in angular momentum.

These laws became central to rigid-body mechanics, from spinning tops and gyroscopes to spacecraft attitude control and engineering structures. Euler developed the framework roughly half a century after Newton’s laws appeared, helping turn particle mechanics into a systematic theory of extended bodies.

Euler’s laws do not contradict Newton’s laws or replace them in ordinary mechanics. They apply Newtonian principles to the distributed parts of a body and express the resulting force and torque balances in a useful whole-body form. James Clerk Maxwell and Michael Faraday made major contributions elsewhere in physics, but neither is the scientist named by this question.