<![CDATA[This research was motivated by the low mathematics learning outcomes in data presentation in the form of tables among third-grade students at UPT SDN Latsari Tuban. This study aims to describe teacher activities, student activities, and the improvement of mathematics learning outcomes through the implementation of the "Mystery Box" learning media. This study is a Classroom Action Research (CAR) conducted in two cycles, comprising the stages of planning, action, observation, and reflection. The subjects of this research were 27 students of class III-A at UPT SDN Latsari Tuban. Data collection techniques included observation, tests, interviews, and documentation, while the data were analyzed using descriptive quantitative and qualitative methods. The results showed that teacher activity increased from 83.75% (Good category) in Cycle I to 96.25% (Very Good category) in Cycle II. Student activity increased from 75.06% (Developing) to 84% (Competent). Learning outcomes also improved, as indicated by the increase in the average score from 72.59 in the pre-cycle to 79 in Cycle I and 90 in Cycle II. The percentage of students reaching the competent and proficient categories increased from 33.3% in the pre-cycle to 66.7% in Cycle I and 85.2% in Cycle II, thereby exceeding the research success indicator of 80%. Consequently, the implementation of the Mystery Box learning media in mathematics learning is proven to improve the learning outcomes of third-grade students at UPT SDN Latsari Tuban.]]>
