Perkembangan teknologi informasi menimbulkan tantangan keamanan data, terutama pada Wireless Sensor Network (WSN) yang rentan terhadap penyadapan. LoRa (Long Range) sering digunakan dalam WSN, tetapi memiliki kelemahan dalam keamanan komunikasi antar node. Untuk mengatasi hal ini, diperlukan sistem autentikasi yang kuat, seperti manajemen kunci. Algoritma ElGamal dipilih karena keamanannya berbasis logaritma diskret dan fleksibilitasnya dalam pengaturan ukuran kunci. Penelitian ini mengimplementasikan Algoritma ElGamal pada WSN dengan LoRa sebagai media transmisi. Perangkat yang digunakan adalah ESP32 Devkit V1 dan LoRa Ra-2 SX1278 pada node master, serta sensor HC-SR04 dan Flame Sensor pada node slave. Hasil menunjukkan Algoritma ElGamal mencapai ketepatan 100% dalam pengiriman data dengan delay 0,289 detik. Daya tahan baterai mencapai 2 jam 58 menit 38 detik. Pengujian intrusi membuktikan Algoritma ElGamal mampu mengamankan data melalui enkripsi dan dekripsi. Kesimpulannya, implementasi Algoritma ElGamal berhasil menjaga keamanan komunikasi dalam WSN, memastikan keaslian pesan, serta menjaga kinerja perangkat selama proses pengiriman dan penerimaan data.   ABSTRACT   The advancement of information technology presents data security challenges, especially in Wireless Sensor Networks (WSN), which are vulnerable to eavesdropping. LoRa (Long Range) is commonly used in WSN but has weaknesses in securing node communication. To address this, a strong authentication system is required, such as key management. The ElGamal algorithm is chosen for its security based on discrete logarithms and flexibility in key size configuration. This study implements the ElGamal algorithm in a WSN system using LoRa as the transmission medium. Devices used include the ESP32 Devkit V1 and LoRa Ra-2 SX1278 on the master node, along with the HC-SR04 sensor and Flame Sensor on the slave node. Results show that the ElGamal algorithm achieves 100% accuracy in data transmission with a delay of 0.289 seconds. The battery lasts for 2 hours, 58 minutes, and 38 seconds. Intrusion testing proves that the ElGamal algorithm secures data through encryption and decryption. In conclusion, implementing the ElGamal algorithm successfully ensures secure communication in WSN, maintains message authenticity, and sustains device performance during data transmission and reception.