Udaykrishna–Sibi K. Thomas is an Indian screenwriting duo known for their works in Malayalam cinema.^[1] Most of their works are in the comedy, action crime film and mass genre. They wrote films such as Mattupetti Machan (1998), Udayapuram Sulthan (1999), Dhosth (2001), C.I.D. Moosa (2003), Runway (2004), Kochi Rajavu (2005), Thuruppu Gulan (2006), Twenty:20 (2008), Pokkiri Raja (2010),Kaaryasthan(2010),Christian Brothers (2011) Mayamohini (2012),Mr. Marumakan(2012), Kammath & Kammath(2013)Rajadhi Raja(2014) and Ivan Maryadaraman(2015).^[2]

The duo parted in 2015. Udayakrishna continued as a scriptwriter. Udayakrishna's first script as a solo writer was Pulimurugan (2016) which became the first Malayalam film to gross over ₹100-150 crore and became the highest-grossing Malayalam film.^[3]

Both Udayakrishna and Sibi started their careers as assistant directors. Sibi assisted Balu Kiriyath and Sandhya Mohan, while Udayakrishna assisted screenwriter A.R.Mukesha and was assistant director under Balu Kiriyath, Ali Akbar, K. Madhu and Venu B. Nair.^[4] Manoj K. Jayan prodded them into a partnership and agreed to star in their directorial debut.^[4] However, that project did not work out. Subsequently, they wrote their first script, Hitler Brothers (1997), for Sandhya Mohan, followed by Mayajalam for Balu Kiriyath. Both films failed at the box office.^[4] The duo's first hit came through Mattuppetti Machan directed by Jose Thomas, followed by Udayapuram Sulthan.^[4] Then came Sundra Purushan, which was a moderate success.

It was followed by Rajasenan's successful movies, Darling Darling and Malayalimamanu Vanakkam. C.I.D. Moosa, was a success. They associated with Johny Antony in most of his directorial ventures thereafter, including the commercially successful Kochi Rajavu and Thuruppu Gulan.^{[citation needed]} They worked with veteran director Joshiy in Runway, Lion and July 4, and in the landmark Malayalam film Twenty:20. Twenty:20 was produced by Association of Malayalam Movie Artists in association with Dileep's Grand Productions and starred most major actors of Malayalam cinema. The film became the highest grossing Malayalam film of all time and brought appreciations for Udayakrishna and Sibi.^[5]

Twenty:20 was followed by Ee Pattanathil Bhootham, which was panned by the critics and an average grosser. In 2010, they made a comeback with Pokkiri Raja, which went on to become a big success and the highest-grossing film of the year.^[6] However, critical responses for Pokkiri Raja were mostly mixed. They scripted debutante Thomson K. Thomas's Kaaryasthan. Despite negative reviews from critics, the film closely followed Pokkiri Raja in collection records of the year.^[6] Their only film in 2011 was Christian Brothers with Joshiy, which became a success.^[7][8][9] They scripted two films in 2012, Mayamohini and Mr. Marumakan. The former was a success and was among the highest-grossing films of the year while the latter, despite heavy criticism, became an average hit. The last release in their combination is Ivan Maryadaraman.

Later in 2016, Udaykrishna wrote script for Pulimurugan directed by Vysakh which was second highest-grossing Malayalam film of all time.Then he wrote scripts for Masterpiece (2017) directed by Ajai Vasudev and Aanakkallan (2018) directed by Suresh Divakar both received mixed reviews but were commercial success. In 2019 he scripted Madhura Raja which was a spin-off to Pokkiri Raja. Even though it received mixed to positive reviews, and it grossed 100 crores from box office.^[10] In 2022, he wrote two scripts for Mohanlal starring films Aaraattu directed by B. Unnikrishnan and Monster directed by Vyshakh. Both films became box-office flops.^[11] In 2023, he scripted two films for Christopher which was directed by B. Unnikrishnan and starred Mammootty in the lead role and Bandra which was directed by Arun Gopy and starred Dileep and Tamannaah Bhatia in the lead role. Christopher received mixed reviews from critics.,^[12] while Bandra received mixed reviews and it is underperformed at the box office.^[13]

Udaykrishnan is married to Manju and has a son. Sibi is married to Jisha and has a son and daughter.^[14]

• Udayakrishna at IMDb
• Siby K. Thomas at IMDb
• "Interview: Udayakrishna-Siby K. Thomas". Varnachithram.
• "Video interview: Udayakrishna-Siby K. Thomas". IndiaGlitz. 14 April 2007. Archived from the original on 27 April 2007.