The LOFAR2.0 Ultra Deep Observation (LUDO) will obtain a single ultra-deep observation of the Euclid Deep Field North with the LOFAR2.0 HBA system, using the international baselines to provide an angular resolution of ∼ 0.3 arcsec, and with a target rms noise level of 2 𝜇Jy/beam at 150 MHz. With this, we will detect, and measure the resolved properties of, star formation in galaxies out to high redshift, and robustly separate the AGN and star-forming components in galaxies to provide a clean measure of both. In conjunction with the exquisite ancillary data from Euclid at matched sub-arcsecond resolution, LUDO's supremely deep data will open a wealth of science goals.