Musical theatre lyricist and composer Stephen Sondheim pioneered the sophisticated characterisation of emotional complexity in the second half of the 20th Century. His work embodies the postmodern perspective, which views identity as a fluid, multi-faceted construct, disconnected from totalising homogenous structures. It is against this background that my thesis aims to investigate Sondheim’s methods of identity construction. In my analysis I will discuss key songs and self-revelatory moments in the musicals Company, A Little Night Music, Sweeney Todd- the Demon Barber of Fleet Street and Into the Woods, focusing on lyrical and musical characterisation, while considering the performative and constructive layers of identity. My results show that Sondheim sets himself musical, structural and stylistic limitations with the sole purpose of breaking them. Thus, he allows his characters to develop beyond their pre-determined narratives and constructing their identities in the process.