This study explores identity motives for using a microblogging site (Twitter) among Internet users in Saudi Arabia and the UK. The former boasts the world's highest per capita use of Twitter, which provides a forum in which users have more opportunity for self-expression than they do in the offline world, and is not subject to the heavy censorship which the Saudi government imposes on other Internet content [1]. Approximately 5000 tweets from the period April-May 2013 were coded and analyzed, using Motivated Identity Construction Theory as a conceptual framework [2]. This theory proposes six universal identity motives of meaning, belonging, continuity, distinctiveness, efficacy, and self-esteem. We consider these motives in turn, and examine their relative prominence in an online context. Support was found for all six universal motives, but the relative prominence of motives and the ways in which they were pursued appeared to depend on the affordances of both the OSN in question, Twitter and the cultural context in which the user was posting: Saudi users appeared to seek distinctiveness, whereas for British users, belonging was a more salient motive. Themes related to meaning, efficacy, and self-esteem were detected frequently, whereas themes related to continuity were less apparent.