Introduction Lipomas are common benign mesenchymal tumours composed of mature adipocytes, most frequently found on the trunk and extremities. Oral cavity lipomas represent less than 5% of all lipomas, with the tongue being a rare site of occurrence. Although typically slow-growing and asymptomatic, tongue lipomas can cause functional impairment depending on their size and location. Aims To present a rare case of a tongue lipoma causing speech disturbance. Methods A 66-year-old patient presented with a 12-month history of a progressively enlarging mass on the ventral surface of the left side of the tongue, associated with increasing speech difficulty. There were no symptoms of dysphagia, odynophagia, dysgeusia or respiratory distress. Examination revealed a soft, mobile, ovoid submucosal mass without overlying mucosal changes or tenderness. The lesion did not cross the midline. Ear, nose, and throat examination was otherwise unremarkable. MRI demonstrated a well circumscribed, homogenous 22x25x26mm mass with fat density, consistent with a lipoma. Differential diagnosis included lipoma, liposarcoma, granular cell tumour and schwannoma. The lesion was excised under general anaesthesia. Intraoperatively, the lesion had a classic yellow, lobulated appearance consistent with a lipoma. It was easily dissected from surrounding tissue and excised in total. Results Postoperatively, the patient recovered uneventfully with immediate improvement in speech clarity. Histopathology confirmed the diagnosis of a simple lipoma composed of mature adipose tissue, with no atypia or evidence of malignancy. Conclusions Although rare, lipoma should be considered in the differential diagnosis of painless tongue mass. MRI should be performed to characterise the mass and evaluate its extent prior to excision. Complete surgical excision is curative and associated with excellent functional recovery and low recurrence rates.