Authentic tasks replicate real-world challenges and standards of performance that experts or professionals typically face in the field. The term “authentic assessment” was first coined by Grant Wiggins in K‒12 educational contexts. Authentic assessment is an effective measure of intellectual achievement or ability because it requires students to demonstrate their deep understanding, higher-order thinking, and complex problem solving through the performance of exemplary tasks. Hence authentic assessment can serve as a powerful tool for assessing students’ 21st-century competencies in the context of global educational reforms. The review begins with a detailed explanation of the concept of authentic assessment. There is a substantial body of literature focusing on the definitions of authentic assessment. However, only those that are original and relevant to educational contexts are included.. Some of the criteria for authentic assessment defined by the authors overlap with each other, but their definitions are consistent. A comparison of authentic assessment and conventional assessment reveals that different purposes are served, as evidenced by the nature of the assessment and item response format. Examples of both types of assessments are included. Three major themes are examined within authentic assessment research in educational contexts: authentic assessment in educational or school reforms, teacher professional learning and development in authentic assessment, and authentic assessment as tools or methods used in a variety of subjects or disciplines in K‒12 schooling and in higher education institutions. Among these three themes, most studies were focused on the role of authentic assessment in educational or school reforms. Future research should focus on building teachers’ capacity in authentic assessment and assessment for learning through a critical inquiry approach in school-based professional learning communities or in teacher education programs. To enable the power of authentic assessment to unfold in the classrooms of the 21st century, it is essential that teachers are not only assessment literate but also competent in designing and using authentic assessments to support student learning and mastery of the 21st-century competencies.