The company said the two appointments would help push Samsung's mobile division to be "the leading content and service provider in the UK mobile industry".
Bulat will roll out Samsung's "Smartphone for everyone" strategy across its UK mobile division, while O'Brien will focus on content.
Simon Stanford, Samsung Mobile UK & Ireland managing director, said: "We continually strive for market leadership with our exceptional innovation pipeline and are committed to developing a marketing and content strategy that provides customers with relevant and engaging experiences with our brand.
"Batyr has solid brand-marketing experience developed in global blue-chip consumer businesses, and Keith brings a wealth of content development strategy to Samsung Mobile’s management team. This is an exciting time for the business."
Before joining Samsung, Bulat worked as the category marketing director for Unilever, where he managed Persil, Surf, Comfort, Harpic and Finish. Prior to Unilever, he spent 10 years at Reckitt Benckiser, rising to global brand marketing director in the UK.
O'Brien joins following three years at FoneStarz, where he held the position of director and general manager, with responsibility for business development. Prior to that, he spent five years at Vodafone as head of music at Vodafone UK, and then as the head of content at Vodafone Australia, where he developed the Vodafone live! content business.
its new riva to the Apple iPad, the Samsung Tab.