Abstract: Techniques are described herein that are capable of identifying patients based on immutable characteristics. For instance, each patient identifier is based on immutable characteristics of the patient who is to be identified by that patient identifier. Examples of an immutable characteristic of a patient include but are not limited to the patient's first name, the patient's last name, the patient's birth date, the patient's birth city, the patient's birth state, the patient's birth country, the patient's mother's maiden name, the patient's gender, etc. For instance, portions of a patient identifier that identifies a patient may be based on respective subsets of immutable characteristics of the patient. Logical operations may be performed with respect to the respective portions of the patient identifier to determine a checksum identifier to facilitate detection of an error with respect to reproduction (e.g., scanning, manually typing, etc.) of the patient identifier.