Regular expression is a formula for searching for the pattern of a sentence or string. Data validation is one of the factors to avoid incorrect input from users. In the buduran village population system, there are various important data that must be valid when it will be stored into the system such as personal data including nik, full name, date of birth and others. The Population System has its drawbacks when inputting citizen data, users can enter any value into the input, of course, this is at risk of errors or errors in the data to be stored. In order to reduce errors in entering data Regular Expression can be an alternative by applying patterns that can validate input from users so that the data to be entered is in accordance with the system request. In this final project, we will discuss the application of the Regular Expression pattern and how it is implemented in the program.