Entropy-Driven Ring-Opening Polymerisation represents an attractive mechanism to produce high-performance polymeric materials as it can be performed using neat, low-viscosity precursors and without the production of by-products or release of volatiles. Macrocyclic oligomers (MCOs) of polyether ketone ketone (PEKK) were synthesised and investigated as an in situ method of forming this high-performance thermoplastic. Cyclic oligomers were successfully synthesised by pseudo-high dilution methods, and the reaction conditions were optimised through careful addition of starting materials and carbonate base selection. These novel compounds were characterised, X-ray crystal structures were obtained, and the synthesis method was extended from the homopolymers to MCOs with the structural isomers predominantly used in industry. PEKK formed from MCOs were characterised by DSC, TGA and GPC and found to have similar glass transitions and molecular weight averages to those of a commercial PEKK polymer.