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tokens: tend to have the steepest radio spectra (), pointing to another possible bias against finding fast-spinning MSPs in ongoing surveys, which focus on central observing frequencies around 350 MHz (Deneva et al. 2013 ; Stovall et al. 2014 ) and 1.4 GHz (Cordes et al. 2006 ; Keith et al. 2010 ; Barr et al. 2013 ). As a result, radio pulsation searches at frequencies below 300 MHz have the potential of opening up a so far largely unexplored parameter space, in the cases where IISM scattering is low and eclipsing does not hinder detection either. Here, we present the discovery of PSR J0952−0607, a very-steep-spectrum MSP, which is now the fastest-spinning neutron star known in the Galactic field (outside of a globular cluster). PSR J0952−0607 was found in a radio pulsation survey using the Low-Frequency Array (LOFAR; Stappers et al. 2011 ; van Haarlem et al. 2013 ) to target unassociated Fermi γ -ray sources. This Fermi -targeted approach has been successful in finding many new MSPs (Ray et al. 2012 ), but our survey is the first to use LOFAR to survey at observing frequencies of 135 MHz (see also Pleunis et al. 2017 ). To enable this survey, a combination of coherent and incoherent dedispersion has been employed to limit the effects of dispersive smearing (Bassa et al. 2017 ). In Section 2 , we will highlight the discovery and multi-wavelength follow-up, with the results being presented in Section 3 . We discuss the broader implications of PSR J0952−0607's discovery and conclude this manuscript in Section 4 . 2. Observations and Analysis 2.1. Radio PSR J0952−0607 was discovered as part of an ongoing LOFAR survey at 135 MHz, continuing on the pilot survey by Pleunis et al. ( 2017 ). Unassociated γ -ray sources were selected from an all-sky source list based on seven years of Fermi -Large Area Telescope (LAT; Atwood et al. 2009 ) Pass 8 data. That list resulted from a preliminary version of the procedure that will be used to produce the next public release LAT source catalog. Among these is a new γ -ray source that has a test statistic of and a relatively small error radius of . The source’s γ -ray spectrum is strongly curved, peaking at 1.4 GeV, and no significant γ -ray emission is detected above 10 GeV. As the source lies well out of the plane (), these characteristics made it a prime millisecond pulsar candidate. The γ -ray source was observed for 20 minutes on 2016 December 25 with LOFAR. The high-band antennas (HBAs) from the innermost 21 LOFAR core stations (longest baseline of 2.3 km) were used to form seven tied-array beams ( FWHM), each covering a 39 MHz wide band centered at 135 MHz. This setup is identical to that of Pleunis et al. ( 2017 ). The complex voltage output for each tied-array beam—in the form of 200 Nyquist-sampled, dual-polarization subbands of 195 kHz each—was processed using GPU-accelerated software to perform coherent dedispersion and channelization with cdmt (Bassa et al. 2017 ) at steps of 1 pc cm −3 between dispersion