This Consensus Statement provides a comprehensive overview of long non-coding RNAs (lncRNAs), addressing their definition, nomenclature, conservation, expression, phenotypic visibility, structure, and functions. LncRNAs, which are transcripts longer than 200 nucleotides, are transcribed by RNA polymerases I, II, and III and include RNAs from processed introns. They play crucial roles in various cellular processes, including cell differentiation, development, and physiological functions, often through interactions with chromatin-modifying complexes, enhancers, and phase-separated nuclear condensates. The statement highlights the challenges in classifying and understanding lncRNAs due to their rapid evolution, cell-type specificity, and modular structures rich in repeats. It also discusses the importance of lncRNAs in gene regulation, epigenetic processes, and the spatial control of gene expression. The authors recommend recognizing lncRNA loci as bona fide genes and suggest strategies for advancing the understanding of lncRNA functions, including high-depth sequencing and targeted experimental approaches.This Consensus Statement provides a comprehensive overview of long non-coding RNAs (lncRNAs), addressing their definition, nomenclature, conservation, expression, phenotypic visibility, structure, and functions. LncRNAs, which are transcripts longer than 200 nucleotides, are transcribed by RNA polymerases I, II, and III and include RNAs from processed introns. They play crucial roles in various cellular processes, including cell differentiation, development, and physiological functions, often through interactions with chromatin-modifying complexes, enhancers, and phase-separated nuclear condensates. The statement highlights the challenges in classifying and understanding lncRNAs due to their rapid evolution, cell-type specificity, and modular structures rich in repeats. It also discusses the importance of lncRNAs in gene regulation, epigenetic processes, and the spatial control of gene expression. The authors recommend recognizing lncRNA loci as bona fide genes and suggest strategies for advancing the understanding of lncRNA functions, including high-depth sequencing and targeted experimental approaches.