Purpose of study: Systemic lupus erythematosus (SLE) is an autoimmune disease affecting all body organs. Beside genetic, hormonal and environmental variables, unbalance between pro-inflammatory and anti-inflammatory cytokines causes alteration of the immune system and promote tissue damage .Interleukin 26 is a pro inflammatory cytokine that has a function in the pathophysiology of autoimmune diseases like SLE .The aim of this study was to assess the level of interlekin-26 in SLE patients and correlate IL-26 with SLE activity. Basic procedures: The study was conducted on eighty five subjects : 20 seemingly healthy individuals as control group and 65 SLE patients, they were subdivided into 2 subgroups ( SLE patients in active state and SLE patients in inactive state). SLE patients were diagnosed according to The European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) 2019 criteria for SLE . Interleukin 26 level was assessed by EIA method. Main findings: results revealed that patients with SLE showed statistically significant higher IL-26 levels than control group and SLE patients in active state had statistically significant higher IL-26 levels than SLE patients in inactive state. Also, significant positive correlation between IL-26 and (SLEADI score, A/C ratio, ESR and Anti –ds DNA) and significant negative correlation between IL-26 and (C3 and C4). Principle conclusion: The findings of this study showed correlation between IL-26 and SLE activity, therefor measurement of IL-26 can help in assessment of SLE activity. Also IL-26 may be useful marker in predicating lupus nephritis because IL-26 serum level correlated positively with A/C ratio.