Use 'fallacious' to question the validity of an argument or information. The politician's promises were fallacious; they contradicted known facts.
Pro Tip 2/3
Not Always Intentional
'Fallacious' doesn't always imply someone is deliberately deceiving; it can be an honest mistake. The scientist acknowledged that his fallacious conclusion was due to an error in his calculations.
Pro Tip 3/3
Academic Context
'Fallacious' is often used in educational settings to critique logic or evidence. Your thesis has a strong foundation, but this point here is based on fallacious assumptions.