Lakes make up to 6% of the Arctic surface area and potentially represent a globally relevant sink/source of carbon. However, constraints on sedimentary organic carbon (OC) stocks and burial rates for Arctic lakes are geographically and temporally limited, particularly for postglacial lakes that have formed in the footprint of prior ice sheets. These data are vital to understand how existing or new lakes that will form as ice sheets melt today may contribute to storing or emitting OC in a warmer world. Here, we compile a suite of high-resolution and well-dated Holocene OC burial rate records (g m-2 yr-1) from Iceland that span a variety of lake systems and catchment sizes. We compare these data with Holocene OC burial rates from Icelandic fjord, marine shelf, peat, and soils to contextualize the relative efficiency of lake OC burial. Our results demonstrate that Icelandic postglacial lakes are orders of magnitude more efficient at sequestering OC than any other sedimentary archive. As fjord, marine shelf, and peat sediments are often cited as relatively large sinks of high-latitude OC burial, our data highlight that postglacial lakes are a critical component of the global carbon cycle on glacial-interglacial timescales.