立陶宛人

立陶宛 (Lìtáowǎn) is the standard transliteration of Lithuania, and the suffix 人 ('person') turns any country name into its nationality: 中国人 Chinese, 美国人 American, 立陶宛人 Lithuanian. Lithuanians are the dominant ethnic group of Lithuania, mostly Catholic, with diaspora communities in the US, Canada, and Poland.

Country + 人 is a fully productive pattern in Chinese, once you can name the country, you can name the nationality with no extra vocabulary.