A system for aligning a pile during pile driving, comprising: a pile (16) having a laterally protruding coupling (20) for a tether; and a pile guide (10) for supporting the pile as it is driven into a substrate, comprising a base frame (12) and a pile guide member (14) mounted on the base frame (12), the pile guide member (14) having in its periphery a slot (24) which is configured to allow the laterally protruding coupling (20) to pass therealong as the pile (16) passes through the pile guide; wherein the pile and pile guide member comprise two pairs of slidably interfitting profiles (52, 86) which are configured to resist gaping in the slot (24) of the pile guide member (14) as the pile (16) is driven therethrough into the substrate.