We have genetically linked the catalytic domain of the CYP79A1 from the plant S. bicolor to the PSI subunit PsaM in Synechococcus sp. PCC 7002 with the aim to target the CYP79A1 to the vicinity of PSI to obtain light-driven P450 biosynthesis. The PsaM-CYP79A1 fusion protein was found to be located in the thylakoids of the cyanobacterial host with a smaller fraction directly attached to the PSI complex. The fusion protein was functional in vivo with the CYP79A1 enzymatic activity being sustained by endogenously produced R428 tyrosine and the product, phydroxyphenylacetaldoxime, being excreted into the growth medium. Through in vitro assays, the enzymatic reaction was confirmed to be light-driven, indicating that the electrons powering the PsaM-CYP79A1 catalytic cycle were indeed photosynthetic electrons delivered from PSI. Cytochrome P450s are key enzymes in the biosynthesis of the majority of the numerous bioactive specialized metabolites with medicinal properties produced by plants. For many of these compounds, the biosynthesis in the plants is tightly regulated with the production levels often being low or highly variable, dependent on induction by abiotic or biotic factors and confined to specific growth stages and cell types, thus making extraction, purification and separation from structurally similar compounds a challenge. This study demonstrates that it is possible to express plant P450s in the thylakoids of a cyanobacterium to obtain a light-driven production system as an environmentally friendly alternative to production through chemical synthesis. As the P450 fold is highly conserved, and since delivery of electrons from PSI to both the CYP79A1 from S. bicolor and the CYP124 from M. tuberculosis via Fd have been shown to function in vitro, it is probable that the light-driven biosynthesis approach is generally applicable to a variety of P450s. For a pathway containing multiple enzymes, the flux through the pathway will be important to optimize. This can be approached by adjusting the relative expression level of the enzymes, e.g. by changing promoters and ribosome-binding sites, and increasing the product channelling, which may be improved e.g. by scaffolding of the enzymes. Balancing the protein expression can however be a challenge, as engineering of cyanobacteria is still not as well established as engineering of classic model microorganisms such as E. coli, which has a less complex metabolism, and even characterized genetic elements can result in unpredictable expression levels. In this study, we have engineered a fusion enzyme of the catalytic domain of a plant P450 and a PSI subunit and expressed it in Synechococcus sp. PCC 7002. The PsaM-CYP79A1 fusion enzyme is present in the thylakoids and proved to be functional with light-driven enzymatic activity detected both in vivo and in vitro. The biosynthesized oxime was found to be excreted into the growth medium, enabling easy product isolation. These works demonstrate the possibility of functionally coupling plant enzymes requiring electrons in their reactions to PSI and utilize.