This research analyzes the impact of a regional brand ambassador and social media advertising on the brand trust and brand loyalty of Lazada, an online marketplace in Indonesia, directly and indirectly. The statistical technique is SEM-PLS to analyze 100 data using convenience sampling. The results show that social media advertising impacts brand trust directly and indirectly, and only brand trust impacts brand loyalty, while the regional brand ambassador does not impact brand trust or brand loyalty directly and indirectly. It implies that Lazada needs to do in-depth research to analyze the right brand ambassador that suits customers' preferences and produces more engaging advertising content to increase brand trust and build brand loyalty.