Gastric cancer (GC) remains a major public health issue as the second leading cause of cancer-related death and the fourth most common cancer worldwide. Although much progress has been achieved in recent years, the early diagnosis and treatment for GC are not yet satisfactory; thus, the prognosis remains poor. Therefore, identification of novel molecules for early diagnosis, prognosis, and treatment is urgently needed. Long non-coding RNAs (lncRNAs) are a new class of non-coding RNAs that participate in a variety of biological processes such as cell proliferation, cell cycle, differentiation, and apoptosis, mainly by regulation of gene expression at various levels, including chromatin, splicing, transcriptional, and post-transcriptional levels. Some lncRNAs are upregulated in cancer and possess oncogenic properties, while others exhibit aberrant low expression and act as tumor suppressors. In this review, we overview the functional roles and regulatory mechanisms of lncRNAs in GC and evaluate their diagnostic, prognostic, and therapeutic values.