There is a lot of evidence in support of the general theory of relativity, and no observation has ever been made which is contrary to it. The most important piece of evidence are:
1. The precession or the orbit of Mercury the closest planet to the Sun. Mercury orbits the Sun in an ellipse. The point of its orbit furthest from the Sun - the perihelion - moves by 43 seconds of arc per century. This is explained in a calculation made by Einstein himself to test the theory.
2. Gravitational redshift. Light is redshifted on moving up a tower, verified in 1959 by Pound and Rebka.
3. Time dilation.
3. Bending of light in a gravitational field. Verified by Eddington in 1915 during a solar eclipse.
4. Time dilation in the presence of a gravitational field. , confirmed in the 1970s.
5. Gravitational waves, verified in 2016.