Deep-ocean (> 2000 m) hydrographic observations are limited to sparse ship-board hydrographic sections repeated every decade and short-lived moored arrays of confined spatial coverage. Upper-ocean (< 2000 m) sampling, largely carried out by the conventional Argo array, has much higher resolution in space and time. The need for more intensive sampling in the deep ocean has been widely recognized by the scientific community. The development of deep profiling Argo floats, a new generation of autonomous instruments capable of diving and recording temperature and salinity down to 4000 to 6000 m depth, is underway. A Deep Argo Workshop was organized to initiate science and implementation planning for a global Deep Argo array, to satisfy broad-scale requirements for measurement of temperature, salinity, and ocean circulation and for combination with other observing system technologies that will complement the float array’s large-scale attributes. The main objectives of the Workshop were: 1. Articulate key scientific issues for Deep Argo: (i) closing the heat, freshwater, and sea level budgets, (ii) characterizing decadal variability in deep ocean water masses, (iii) estimating the mean and decadal variability in deep ocean. circulation including meridional overturning circulations. 2. Determine sampling requirements to achieve Deep Argo objectives. 3. Refine plans for the deployments of Deep Argo pilot arrays. 4. Promote international collaboration within the Deep Argo community. Early results of deep float deployments and research plans for Deep Argo regional pilot arrays were presented.