Organic materials have the potential to be the basis for environmentally friendly, all-carbon electronics. However, most real devices require additional materials, such as metals for electrodes. Here, we present an example of all-organic devices: organic electrochemical transistors (OECTs), which are fully printed and do not use metal electrodes. We prove that these OECT devices have state-of-the-art performance and present three applications using poly(benzodifurandione) (PBFDO) for the electrodes and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) for the active material: (i) a PBFDO strain sensor made from a single material, which demonstrates real-time finger flexion detection; (ii) an OECT-based ion sensor for monitoring the concentration of sodium chloride (NaCl) in aqueous environments; and (iii) intrinsically stretchable, all-organic OECTs that can stretch up to 60% without the use of elastomeric additives or structural engineering.