We present the ICLE-RC, a corpus of learner English texts annotated for relative clauses and related phenomena. The corpus contains a collection of 144 academic essays from the International Corpus of Learner English (ICLE; Granger et al., 2002), representing six L1 backgrounds – Finnish, Italian, Polish, Swedish, Turkish, and Urdu. These texts are annotated for over 900 relative clauses, with respect to a wide array of lexical, syntactic, semantic, and discourse features. The corpus also provides annotation of over 400 related phenomena (it-clefts, pseudo-clefts, existential-relatives, etc.). Here, we describe the corpus annotation framework, report on the IAA study, discuss the prospects of (semi-)automating annotation, and present the first results from our corpus analysis. We envisage the ICLE-RC to be used as a valuable resource for research on relative clauses in SLA, language typology, World Englishes, and discourse analysis.