According to our current understanding of physics, the maximum theoretical escape velocity for an object with mass is the speed of light in a vacuum, denoted by "c." In other words, no object with mass can attain or exceed the speed of light without violating the laws of the universe as we currently understand them.
The concept of escape velocity is based on the idea that in order for an object to escape the gravitational pull of a massive body, such as a planet or a star, it needs to achieve a certain velocity. This velocity is calculated based on the mass of the body and its radius.
However, as an object with mass approaches the speed of light, its relativistic mass increases, and it would require an infinite amount of energy to accelerate the object to reach or exceed the speed of light. This is in accordance with Einstein's theory of relativity, which indicates that it is impossible for any object with mass to reach or surpass the speed of light.
Therefore, the maximum theoretical escape velocity for an object with mass, within the boundaries of our current understanding of physics, is the speed of light, which is approximately 299,792,458 meters per second (or about 186,282 miles per second).