Greater competition from Chinese smartphone manufacturers and a lack of a successor to the Note 7 has slowed Samsung's smartphone sales, new research has found.
The Galaxy manufacturer has retained its top slot among smartphone manufacturers in the first quarter of this year, with sales of 78.7 million.
However, its market share fell from 23.3 percent 12 months ago to 20.7 percent, while sales slid 3.1 percent.
Anshil Gupta, Research Director at Gartner, said: "Although Samsung announced that preorders for the Galaxy S8 and S8 Plus are up 30 percent year on year, the absence of an alternative to Note 7 and the fierce competition in the basic smartphone segment are leading Samsung to continuously lose market share.
"Sales of iPhones were flat, which led to a drop in market share year on year. Similar to Samsung, Apple is increasingly facing fierce competition from Chinese brands Oppo and Vivo, among others, and its performance in China is under attack."
Oppo almost doubled its smartphone sales during the 12 months, from 15.9 million to 30.9 million.
It now has an 8.1 percent market share, up from 4.6 percent a year ago, leaving it in fourth place.
Gupta noted the manufacturer was making inroads through its camera and fast-charging features and sales through physical channels.
He said: "Oppo continued to rally sales through a large network of brick-and-mortar retailers, beating market incumbents such as Samsung and Huawei."
Vivo also experienced strong growth, with sales up 84.3 percent to 25.8 million, and a market share of 6.8 percent.
Gupta said: "Vivo saw growing demand of its smartphones from the emerging markets in Asia/Pacific, including India, where sales grew over 220 percent thanks to its increased brand appeal and high-quality smartphones."
Huawei, the third biggest smartphone maker with a nine percent share, saw its recent explosive growth eroded by its Chinese rivals.
Sales grew by 18.4 percent to 34.2 million.
Gupta said: "The top three Chinese smartphone manufacturers are driving sales with their competitively priced, high quality smartphones equipped with innovative features.
"Furthermore, aggressive marketing and sales promotion have further helped these brands to take share from other brands in markets such as India, Indonesia and Thailand."
These Chinese companies were also increasing pressure on second placed Apple, which only had sales growth of 0.70 percent.
It had sales of 51.9 million but market share fell from 14.8 percent to 13.7 percent.
Overall, there were smartphone sales of 380 million in the first quarter, up 9.1 percent on 2016. Android's market share was up by two percentage points to 86.1 percent, driven by the strong growth in sales of Chinese handsets.
Apple's OS share dropped from 14.8 percent to 13.7 percent.
Other operating systems are almost non-existent, with a market share of 0.2 percent and sales of only 821,000.