We develop a novel measure of partisan corporate speech using techniques from natural language processing. Using the entire corpus of tweets from companies listed on the S&P 500, we first establish a large increase in the amount of partisan corporate speech between 2011 and 2022. This increase in partisan speech is disproportionately driven by corporates using speech commonly associated with Democratic politicians; in particular, statements related to climate change as well as diversity, equity, and inclusion. We also explore how intraday stock returns respond to partisan corporate tweets.