Can I be fired for any reason if I do not have an employment contract?

If you did not have an employment contract, you are considered an “at-will employee”, which is the standard in most states. An at-will employee can be terminated for any reason as long as that reason is not discriminatory or retaliatory. So, you cannot be fired for being, for example, a woman or for being disabled or for being pregnant. You also cannot be fired if you engage in certain protected activities such as reporting your employer’s wrongful conduct or opposing workplace discrimination.