Aurachins comprise a small family of natural products featuring a quinoline chromophore, acting as potent inhibitors of respiratory chain electron transport and exhibiting antimicrobial, antifungal and antiplasmodial activities. During a search for bioactive secondary metabolites from microorganisms in special niches, a new aurachin-type compound, aurachin SS (1), together with two known compounds aurachin C (2) and aurachin D (3), was isolated from an earwig (Forficula auricularia)-associated Streptomyces sp. NA04227 via large-scale fermentation and chromatographic separation (normal phase, C-18 silica gel, Sephadex LH-20). The structure of compound 1 was elucidated by HRESIMS and NMR spectroscopy (1H, 13C, HSQC, HMBC, COSY), with a molecular formula of C21H27NO2 and a unique geranyl side chain (distinct from typical aurachins with farnesyl chains). The whole genome of NA04227 was sequenced, and a biosynthetic gene cluster (sau cluster) was identified using antiSMASH, revealing genetic organization similar to known aurachin clusters (aua in Stigmatella aurantiaca, rau in Rhodococcus erythropolis) but with unique genes (e.g., sauK, a thioesterase). A biosynthetic pathway for aurachins in NA04227 was proposed, involving anthranilate activation, polyketide extension, prenylation, hydroxylation, and methylation. Antibacterial assays showed compounds 2 and 3 exhibited potent activity against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, and Micrococcus luteus (MIC 4.0–16.0 μM), while compound 1 displayed moderate activity (MIC 32.0–64.0 μM). In summary, a new aurachin SS with a unique geranyl side chain was isolated and characterized, and its biosynthetic pathway and antibacterial activity, along with two known aurachins, were investigated.