<![CDATA[The low science process skills (SPS) of junior high school students is the main background of this study, especially in the indicator of observing and communicating scientific results. This study aims to analyze the effectiveness of the discovery learning model in improving SPS on the human respiratory system material. Using a quantitative approach with a one-group pretest-posttest design, research subjects were selected through a purposive sampling technique at SMP Negeri 21 Surabaya. The research stages included initial observation through a pretest, providing discovery learning model treatment, and final measurement through a posttest. The results showed that the implementation of learning reached a very high average of 99%. The paired t-test proved a significant difference with a significance value below 0.001. Quantitative data showed an increase in the average value from 54.2 to 81.83 with an N-Gain score of 0.621 which is included in the moderate category. The indicator of planning an investigation achieved the highest increase of 0.718, while the indicator of communicating obtained the lowest score of 0.500. In addition, student responses to this model were very positive with a satisfaction percentage reaching 83.58%. The main conclusion of the study confirms that the application of the discovery learning model effectively improves junior high school students' science process skills in the respiratory system. Educators are strongly advised to implement this model to optimize students' scientific abilities through independent learning experiences, active exploration, and direct concept discovery within the school science education process. ABSTRAK Rendahnya keterampilan proses sains (KPS) murid SMP menjadi latar belakang utama penelitian ini, terutama pada indikator mengamati dan mengomunikasikan hasil ilmiah. Penelitian ini bertujuan untuk menganalisis efektivitas model discovery learning dalam meningkatkan KPS pada materi sistem pernapasan manusia. Menggunakan pendekatan kuantitatif dengan desain one group pretest-posttest, subjek penelitian dipilih melalui teknik purposive sampling di SMP Negeri 21 Surabaya. Tahapan penelitian meliputi observasi awal melalui pretest, pemberian perlakuan model discovery learning, dan pengukuran akhir melalui posttest. Hasil penelitian menunjukkan keterlaksanaan pembelajaran mencapai rata-rata sangat tinggi sebesar 99%. Uji t berpasangan membuktikan adanya perbedaan signifikan dengan nilai signifikansi di bawah 0,001. Data kuantitatif menunjukkan peningkatan nilai rata-rata dari 54,2 menjadi 81,83 dengan skor N-Gain sebesar 0,621 yang termasuk kategori sedang. Indikator merencanakan penyelidikan mencapai peningkatan tertinggi sebesar 0,718, sementara indikator mengomunikasikan memperoleh skor paling rendah yakni 0,500. Selain itu, respon murid terhadap model ini sangat positif dengan persentase kepuasan mencapai 83,58%. Simpulan utama penelitian menegaskan bahwa penerapan model discovery learning secara efektif meningkatkan keterampilan proses sains murid SMP pada materi sistem pernapasan. Pendidik sangat disarankan mengimplementasikan model ini untuk mengoptimalkan kemampuan ilmiah murid melalui pengalaman belajar mandiri, eksplorasi aktif, serta penemuan konsep secara langsung dalam proses pendidikan sains di sekolah.]]>
