The visual image of the River Thames was central to the identity of London in the long eighteenth century. Art historical engagement with the subject has been dominated by refined upriver views, especially depictions of sites of royal residence and scenes of pageantry. This focus eclipses a significant untapped body of contemporary Thames imagery which suggests the existence of a more complex relationship between the visualisation of London's river and the larger social, ideological and economic contexts of Britain's rapidly developing global maritime and imperial power. This thesis proposes that only by reconnecting these works with the more familiar visual culture of eighteenth-century maritime London, can the full extent to which the river was identified as a signifier of national and imperial consciousness be fully understood. This identification is most apparent in depictions of the commercial and naval activity in the mercantile environs of the port to the east of London Bridge which effectively constitute a visual concordia discors with aggrandised upriver subjects. Thames imagery is also prevalent in the genre of satire where the countercultural nature of the port, characterised via its stereotypical portrayal of a bawdy labour force, undermines the polite pretensions of high art. In topographical views of the capital the dramatic physical rationalisation of the Thames in terms of new bridges and docks was harnessed to raise the profile of London and its river to that of an efficient cosmopolitan port suited for commercial empire. Above all, the image of the Thames evolved into a powerful and widely understood symbol reflecting a patriotic national identity constructed around maritime trade and naval power. This thesis argues for an alternative, more complex image of the Thames in the long eighteenth century which is informed by a range of ideological issues centred around the meaning of commerce and empire from a period when the river became the emblem of London's increasing self-identification as the centre of a maritime nation of unprecedented scale.