We investigated the potential diagnostic and prognostic role of maternally expressed 3 (MEG-3), a type of long non-coding RNA, in epithelial ovarian carcinoma (EOC) by comparing long non-coding RNA (LNCRNA-MEG-3) expression in EOC and normal ovarian tissues and exploring clinical correlations. The study included 126 patients diagnosed with stage III EOC, confirmed by histopathological examination. We used quantitative polymerase chain reaction (qPCR) to quantify levels of the long non-coding RNA MEG-3. The long non-coding RNA MEG-3 expression in EOC tissues was significantly lower than in normal ovarian tissues, indicating its potential as a diagnostic marker. Receiver operating characteristic curve (ROC) analysis demonstrated an Area under the ROC Curve (AUC) of 0.831, signifying its high sensitivity (100%) and specificity (97.04%) in distinguishing malignant ovarian tissues from normal ones. LNCRNA-MEG-3 expression varied significantly across different EOC stages (p < 0.0001) and tumor grades (p < 0.0001), correlating with aggressive behavior and serous tumor types. Low LNCRNA-MEG-3 expression associated with adverse prognostic factors such as ascites (p < 0.0001) and poor treatment response (p < 0.0001). High LNCRNA-MEG-3 expression predicted better treatment response. It also correlates with the size of residual disease after debulking surgery, which is an important prognostic factor. Compared to those with low LNCRNA-MEG-3 expression, patients with high expression had significantly longer overall and disease-free survival (p = 0.0004 and p = 0.0002, respectively). The study highlights LNCRNA-MEG-3 as a valuable diagnostic and prognostic marker for EOC. Low expression of the long non-coding RNA MEG-3 is linked to aggressive tumor features and unfavorable clinical outcomes, stressing the importance of MEG-3 in managing EOC and tailoring the treatment to the individual patient.