Oh love, apple of my eye), also known as OK Kanmani, is a 2015 Indian Tamil-language romantic drama film written, directed and produced by Mani Ratnam.

[8] O Kadhal Kanmani was released on 17 April 2015 and won positive reviews from critics, praising the lead pair's performances and the quality of the film's technical aspects.

Upon seeing the love and patience that Ganapathy has for his wife Bhavani, an Alzheimer's patient, they begin to understand the importance of each other's presence in their lives.

In early 2014, Mani Ratnam first approached Telugu actor Ram Charan to be a part of the film, but he felt the lead role would not work for him.

[15] In August 2014, Madras Talkies had confirmed that Dulquer Salmaan would play the lead role in their forthcoming production and it was reported that Mani Ratnam's regular collaborator, composer A. R. Rahman would also work on the film.

[23] He revealed it was an urban love story, and added that the Mumbai setting was also justified as it dealt with people away from home who become independent of the rules and regulations of a family.

[25] In a press conference at Taj Coromandel in Chennai, Ratnam said that the film is a contemporary take on the new generation, their attitudes and their values.

[28] The director revealed he first met Dulquer at the audio release function of Vaayai Moodi Pesavum (2014) and felt that he was the right choice to play the character Aadi, although he hadn't seen any of the actor's films.

[29] Leela Samson, a Bharathanatyam dancer and author, was selected to make her acting debut and portray a retired Carnatic singer in the film, appearing as Prakash Raj's wife.

[31] The rest of the cast consisted of Mani Ratnam's assistant directors Sivakumar Ananth and Chandrika Chandran, while his friends Rama Ramasamy, Prabhu Lakshman and the former manager of Sify, John Devasahayam, were given other roles.

[32] A number of rookie actors, who later went onto feature in larger projects, including Arav, Ashwin Kumar Lakshmikanthan, Ciby Bhuvana Chandran and Pavithra Lakshmi made appearances as colleagues of Dulquer's character.

[49] Social media promotions were handled by Chennai-based group, Uptown Ideas, and the film's presence on Facebook and Twitter succeeded in garnering praise and creating anticipation before release.

[50] The team had initially been assigned by Mani Ratnam to handle radio promotions, but consequently also managed online marketing and liaised with the director, sending him ideas of potential campaigns for approval.

[9] Baradwaj Rangan of The Hindu wrote, "O Kadhal Kanmani is something of a greatest-hits package of Mani Ratnam", while also singling out Nithya Menen's performance for praise.

"[58] Anupama Subramanian of Deccan Chronicle wrote, "After a couple of lackluster flicks, master story teller Mani Ratnam is back with a bang with a feel good complete romantic movie O Kadhal Kanmani.

[59] Reviewing for Firstpost, Latha Srinivasan stated, "O Kadhal Kanmani celebrates romance, an emotion that is as old as creation itself (remember Adam and Eve?).

"[60] Udhav Naig of The Hindu said "Ratnam has made a film that will not only resonate with audiences across India but has also truly retained the Tamil flavor".

[61] The critical review board of Behindwoods gave the film 3.25 stars out of 5 stating, "Okay, moral of the story – One fine morning, Mani Ratnam got up and decided to make something special for all young people out there.

Technically OK Kanmani is superior as both AR Rahman and PC Sreeram have given their career best work for Mani Ratnam as the master craftsman himself is in tremendous form.

By throwing the spotlight on modern India's idea of romance, Ratnam has also succeeded in making us root for an older couple madly in love in O Kadhal Kanmani.

[66] R. S. Prakash of Bangalore Mirror wrote, "Mani delves into the plot of live-in relationship, but he has chosen not to go overboard, given the sensitivity of the subject, especially in his part of the world.

"[67] Writing for The Times of India M. Suganth said, "The filmmaker shows that his touch is intact and he can still make a romance come alive on screen."

[68] Indo-Asian News Service stated, "By throwing the spotlight on modern India’s idea of romance, Ratnam has also succeeded in making us root for an older couple madly in love in “O Kadhal Kanmani”.

"[69] S. Saraswathi of Rediff.com gave the film 3.5 out of 5 stars claiming that it has, "director's trademark, unique narrative style, realistic characters, and excellent performances coupled with great music and stunning visuals".

[71][72] In Tamil Nadu, O Kadhal Kanmani grossed nearly ₹6.30 cr in its first three days, opening at second place behind Kanchana 2 and experienced particular success in multiplexes as expected.

The venture managed to gross approximately $714, 000 (₹4.42 crore) from the US market alone, becoming one of the most successful Tamil films of all time in the US, as its acquisition price was very low compared to its business.

[90] A Hindi remake of the film was officially announced in November 2015, with Aditya Roy Kapur and Shraddha Kapoor portraying the lead roles, and directed by Shaad Ali.