Ribonucleotide reductases (RNRs) catalyse the conversion of ribonucleotides to deoxyribonucleotides, utilizing radical chemistry to carry out the reaction. Class I RNRs consist of R1 and R2 subunits: R1 contains the active site and R2 generates and stores a stable tyrosyl radical. The conserved tyrosine where the radical is stored until needed in R1 has previously been believed to be an absolute requirement for R2 activity. The Chlamydia trachomatis R2 lacks this tyrosine and a phenylalanine is present in its place, but the protein is still active. Here, the crystallization of C. trachomatis R2 is described. A heavy-atom co-crystallization approach was used to obtain crystals. Hopefully, the C. trachomatis R2 structure will provide key clues as to how this enzyme is able to function while lacking the features that have previously been believed to be essential for activity.