Fundamental may refer to:
- Fundamental frequency,a concept in music or phonetics, often referred to as simply a "fundamental".
- Fundamentalism, the belief in, and usually the strict adherence to, the simplistic or "fundamental" ideas based on faith of a system of thought. Interestingly not based on the fundamental principles or objectives of a system. i.e. following the word and not the spirit of a law or system.
- Any of a number of fundamental theorems identified in mathematics, such as
- Fundamental analysis, a method that uses financial and economic analysis to predict the movement of security prices such as bond prices, but more commonly stock prices.