Penelitian ini dilandasi oleh rendahnya keterampilan berpikir tingkat tinggi (HOTS) siswa akibat implementasi pembelajaran yang belum optimal serta kurangnya integrasi antar disiplin ilmu dalam proses belajar. Penelitian ini bertujuan untuk menganalisis pengaruh pembelajaran berbasis proyek (Project Based Learning/PjBL) dengan pendekatan STEM (Science, Technology, Engineering, and Mathematics) terhadap peningkatan kemampuan berpikir tingkat tinggi (HOTS) siswa pada materi sistem pertahanan tubuh. Metode dalam penelitian ini menggunakan quasi-experiment dengab desain nonequivalent control group. Sampel dalam penelitian ini diambil secara purposive dengan jumlah 35 siswa kelas eksperimen dan 34 siswa kelas kontrol. Instrumen yang digunakan dalam pengambilan data adalah tes uraian, angket respon siswa, dan lembar observasi pembelajaran. Data hasil penelitian dianalisis secara statistik yang meliputi uji N-Gain, uji normalitas, dan uji homogenitas, serta uji hipotesis (uji t). Hasil analisis menunjukkan bahwa penerapan model PjBL dengan pendekatan STEM berpengaruh signifikan terhadap peningkatan HOTS siswa, khususnya dalam aspek menganalisis (C4), mengevaluasi (C5), dan menciptakan (C6). Dengan demikian, pembelajaran PjBL-STEM dapat dijadikan alternatif strategi pembelajaran inovatif untuk meningkatkan kemampuan berpikir tinggi siswa.

This study is based on the low level of students' high-level thinking skills (HOTS) due to the implementation of suboptimal learning and the lack of integration between disciplines in the learning process. This study aims to analyze the effect of project-based learning (PjBL) with the STEM (Science, Technology, Engineering, and Mathematics) approach on improving students' high-level thinking skills (HOTS) on the body protection system material. The method in this study used a quasi-experiment with a nonequivalent control group design. The sample in this study was taken purposively with a total of 35 students in the experimental class and 34 students in the control class. The instruments used in data collection were presentation tests, student response questionnaires, and learning observation sheets. The research data were analyzed statistically which included the N-Gain test, normality test, and homogeneity test, as well as hypothesis testing (t-test). The results of the analysis showed that the application of the PjBL model with the STEM approach had a significant effect on improving students' HOTS, especially in the aspects of analyzing (C4), disseminating (C5), and creating (C6). Thus, PjBL-STEM learning can be used as an alternative innovative learning strategy to improve students' high-level thinking skills.