Cells in the rodent hippocampal (HP) formation contain representations of space and time. In entorhinal cortex (EC), spatial (grid) cells are organised along a hierarchical gradient with smaller spatial scales dorsal and larger scales ventral (homologous to a posterior-anterior axis in humans). Recent models suggest these patterns of cellular activity might be the consequence of a more general mechanism that optimally represents the structure of possible sequences in the world. If so, it should be possible to find similar signatures for arbitrary (non-spatial) sequences. Using extracellular recordings in epilepsy patients, we show “position in sequence” is also represented in HP/EC cells when subjects are asked to memorise an arbitrary sequence of stimuli. Using fMRI in healthy volunteers (where we can train subjects on long (113 element) sequences with rich hierarchical structure), we show that these sequence positions are represented in a factorised hierarchical form along a posterior-anterior EC gradient, exactly as grid cells are in space. In both cells and fMRI, the EC representation of sequence position was abstracted - it generalised over multiple sequences with different stimuli (analogous to grid cells generalising over multiple environments). Overall, using single-unit recordings and fMRI we show that the human HP formation contains abstracted representations of sequential structures. Moreover, these representations are organized hierarchically along posterior–anterior axis in EC. The hierarchical levels factorised (as with grid cells). Notably, the temporal structure of our daily life is also hierarchical: breakfast-lunch-dinner sequences form days, days form months etc. Thus, similar representational principles of sequence hierarchy and abstraction would permit efficient inferences and generalisations in the experiences that make up every-day life.