) Ohidoa Toluwa

This study examines the relationship between sustainability disclosure and the timeliness of financial reporting among listed firms in Nigeria. In the modern corporate landscape, stakeholders demand transparency regarding Environmental, Social, and Governance (ESG)impacts alongside traditional financial performance. However, Nigerian firms face challenges such as weak enforcement and institutional gaps, leading to delays in reporting and inadequate disclosures. The primary objective of this study is to assess the extent of sustainability disclosure, evaluate compliance with regulatory timelines, and determine if a significant relationship exists between these two variables. The study adopts a descriptive and ex-post facto research design, focusing on companies listed on the Nigerian Exchange Group (NGX). Data are sourced from the annual reports and accounts of selected firms. The study tests three hypotheses centered on 101 the significance of disclosure levels and the correlation between sustainability reporting and reporting speed. Preliminary observations suggest that while awareness is growing, many firms still provide limited sustainability information and often exceed regulatory deadlines. The findings of this27 study will be of significant value to the Financial Reporting Council of Nigeria (FRCN), the Securities and Exchange Commission (SEC), and potential investors by highlighting areas for improved monitoring and enforcement. The study concludes that enhancing the quality and timeliness of disclosures is critical for boosting investor confidence and promoting corporate accountability in the Nigerian emerging market. Keywords: Sustainability Disclosure, Financial Reporting Timeliness, ESG Reporting, Corporate Governance, Nigerian Exchange Group, Transparency.