Robert Mbui (born 29 August 1968) is a Kenyan politician, education entrepreneur and senior opposition leader who has represented Kathiani Constituency in Machakos County since 2013 on a Wiper Democratic Movement (WDM-K) ticket. He currently serves as Deputy Minority Leader in the National Assembly and is Wiper’s national organising secretary, positioning him as one of party leader Kalonzo Musyoka’s key lieutenants in parliamentary strategy and coalition politics. Before his election to Parliament, Mbui chaired the Kathiani Constituency Development Fund (CDF) for the then larger Kathiani (before Mavoko was carved out) from 2008 to 2011, earning national recognition when the fund was rated among the best managed in Kenya and winning a National Taxpayers Association award for best CDF manager in 2011. In Parliament he has served on committees such as Health, Regional Integration, and Procedure and House Rules, and, more recently, has been a visible opposition voice in high-stakes fiscal debates and confrontations over controversial bills—most notably in 2023–2024 budget and privatisation battles where his attempts to block what he termed unconstitutional proceedings even led to temporary suspension from the House. Mbui’s political influence is grounded in a long career in education and management. After early schooling at Kahawa Primary School, he worked as a graduate teacher at Nairobi Milimani Secondary School under the Teachers Service Commission (1991–1994), then as Education Manager at Future Kids (K) Ltd (1994–1997), before founding and directing Mutungoni Academy in Athi River from 1997 to 2013—a period in which the school became one of the area’s notable private institutions. Academically, he holds a Bachelor’s degree (reported in media profiles as from Kenyatta University) and a Master’s in Strategic Management from the Kenya Institute of Management, training that underpins his reputation for organisation, budgeting and constituency project delivery. His honours include the Chief of the Order of the Burning Spear (CBS) awarded on Jamhuri Day 2022 and earlier accolades such as the 2016 Mzalendo Trust recognition and a 2021 County Gala Award for Best MP in the Eastern Region, reinforcing his image as both a loyal Wiper stalwart and one of the more effective development-oriented MPs in the lower Eastern region.