No, it isn't. Evolution is supported by mountains of evidence and is one of the strongest ideas science has ever produced.
Regardless, it's not a scientific fact. Anyone with a background in the sciences would agree.
People with a background in the sciences don't agree with your statement:
H. J. Muller, geneticist and Nobel laureate - "So enormous, ramifying, and consistent has the evidence for evolution become that if anyone could now disprove it, I should have my conception of the orderliness of the universe so shaken as to lead me to doubt even my own existence. If you like, then, I will grant you that in an absolute sense evolution is not a fact, or rather, that it is no more a fact than that you are hearing or reading these words."
Kenneth R. Miller, cell biologist and molecular biologist - "evolution is as much a fact as anything we know in science."
Ernst Mayr, evolutionary biologist - "The basic theory of evolution has been confirmed so completely that most modern biologists consider evolution simply a fact. How else except by the word evolution can we designate the sequence of faunas and floras in precisely dated geological strata? And evolutionary change is also simply a fact owing to the changes in the content of gene pools from generation to generation."
Stephen Jay Gould, paleontologist and evolutionary biologist - "Evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts. Facts do not go away when scientists debate rival theories to explain them. Einstein's theory of gravitation replaced Newton's, but apples did not suspend themselves in mid-air, pending the outcome. And humans evolved from ape-like ancestors whether they did so by Darwin's proposed mechanism or by some other yet to be discovered."
Richard Lenski, evolutionary biologist - "Scientific understanding requires both facts and theories that can explain those facts in a coherent manner. Evolution, in this context, is both a fact and a theory. It is an incontrovertible fact that organisms have changed, or evolved, during the history of life on Earth. And biologists have identified and investigated mechanisms that can explain the major patterns of change."
The rallying cry of "just a theory" is supported primarily by creationists, few of which have backgrounds in science and fewer of which have backgrounds in biology in particular.