Background: Gold nanoparticles are increasingly attracting researchers because of the unique electronic, optical and chemical properties of gold nanoparticles. However, in the manufacture of AuNP chemicals are used can harm the environment, so that in the last few years a green synthesis approach has been developed. Objective: In this study, AuNP was made using kacip fatimah extract which had good characterization and stability. Materials and Methods: The AuNP synthesis uses are 30% HAuCl₄ solution and kacip fatimah extract with concentration of 5%, 10%, and 15% which is stirred for 5 minutes at  speed of 300 rpm, and sodium citrate solution is added as a capping agent. Characterization was carried out using pH meter, UV-VIS spectrophotometer, Particle Size Analyzer (PSA), and Transmission Electron Microscopy (TEM). Stability tests were carried out at AuNP stored at room temperature for 56 days. Results: The result of AuNP synthesis with 5% concentration extract formed at 535.50 nm with 0.720 A absorption, pH 3.83, particle size 59.93±1.35 nm, polydispersity value 0.463±0.06, zeta potential -31.0±7.44 mV, and morphology found spherical, pentagonal, and there are also irregular shapes. In the stability test of AuNP with extract concentrations of 5%, 10%, and 15% for 56 days observed using UV-VIS spectrophotometers and PSA, AuNP with 5% concentration extract had better stability than AuNP with 10% and 15% concentration extract. Conclusion: The synthesis of AuNP using kacip fatimah extract had good characterization and stability at 5% extract concentration stirred for 5 minutes at 300 rpm and added sodium citrate as capping agent.

Key words: Gold nanoparticles, kacip fatimah extract, sodium citrate, optimization, and electron microscopy