Scientific dissent is dissent from scientific consensus. Disagreements can be useful for finding problems in underlying assumptions, methodologies, and reasoning, as well as for generating and testing new ways of tackling the unknown. In modern times, with the increased role of science on the society and the politicization of science, a new aspect gained prominence: effects of scientific dissent on public policies.

Scientific dissent is distinct from denialism, which is a deliberate rejection of scientific consensus usually for commercial or ideological reasons.

Miriam Solomon in her book Social Empiricism argues that scientific dissent is the normal state of scientific inquiry, rather than a conflict that needs resolution. She argues that disagreements between individual scientists about the proper direction of research are not cause for concern, because scientific rationality must be assessed at the level of the scientific community. As long as all theories being pursued yield some unique empirical successes, Solomon argues that their pursuit is worthwhile and consistent with the common view that science aims at truth. In Solomon's view, competing scientific theories can even be inconsistent with one another while each containing some degree of truth. Empirical evidence may not be sufficient to distinguish between competing theories, and successful theories often have core assumptions that are incorrect.

A number of famous scientists have been sceptical of what were, or came to be, mainstream scientific positions. For example, Ernst Mach famously declared in 1897: "I don't believe that atoms exist!" Wilhelm Ostwald expressed a similar scepticism about atoms, but changed his mind in 1908.

In the early 20th century, peptic ulcers were believed to be caused by stress and dietary factors. The physicians Robin Warren and Barry Marshall showed in 1982 that the bacterium Helicobacter pylori was responsible, but the medical community was slow to make appropriate changes in ulcer treatment.

Scientific debate is a healthy and necessary part of science, but scientific debate may collide with power dynamics within the academic world. Suppression of legitimate scientific debate can be considered as a breach of academic integrity. Examples of suppression include journal editors rejecting a paper for political reasons prior to peer-review, refusing access to data for research which might draw negative conclusions about the safety of some commercial product, and putting pressure on a university to fire a dissenting researcher.

In modern times proponents of science denialism, pseudoscience, and conspiracy theories often try to disguise their viewpoints as "scientific dissent" to take an advantage of the benefit of doubt. Such cases are typically recognized by lack of crucial elements of scientific approach: insufficient evidence base, lack of rigor and control, etc.^{[citation needed]}

Lack of discussion of claims coming from fringe science may be presented as suppression by mainstream science. This was described as "manufacturing dissent" and discussed in the context of neo-creationism.