Neural dependency parsing has proven very effective, achieving state-of-the-art results on numerous domains and languages. Unfortunately, it requires large amounts of labeled data, that is costly and laborious to create. In this paper we propose a selftraining algorithm that alleviates this annotation bottleneck by training a parser on its own output. Our Deep Contextualized Selftraining (DCST) algorithm utilizes representation models trained on sequence labeling tasks that are derived from the parser's output when applied to unlabeled data, and integrates these models with the base parser through a gating mechanism. We conduct experiments across multiple languages, both in low resource in-domain and in crossdomain setups, and demonstrate that DCST substantially outperforms traditional selftraining as well as recent semi-supervised training methods. 1 2