Growth stocks can make for excellent investments to simply buy and hold. It can take time for growing businesses to achieve their potential, but if they do, that can result in massive returns for shareholders who hang on.

If you can buy growth stocks at attractive valuations, that can help position you for even greater gains in the long run.

Three growth stocks that cost less than $100 that you'll want to consider adding to your portfolio today include Coupang (CPNG 1.20%), Chipotle Mexican Grill (CMG 1.09%), and Marvell Technology (MRVL 1.36%). Here's why these stocks can be solid long-term buys.

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1. Coupang

At around $30 per share, Coupang is well below the $100 mark. But that doesn't mean this online retail giant hasn't been a good buy. Year to date, it has soared by more than 40%.

What makes the stock a compelling option for growth investors is that the company is the dominant online retailer in South Korea. It has also expanded into Taiwan and looks to be eyeing even more growth. The U.S.-based company also helps American merchants looking to expand into international markets. And its operations extend beyond just e-commerce, as Coupang has a food delivery business, a video streaming service, and it also offers financial services through Coupang Pay.

Coupang isn't highly profitable right now, as in the trailing 12 months, it has reported net income of $365 million on sales totaling $32.3 billion. But its bottom line has been trending in the right direction, and as it continues to scale, that should improve. Its price-to-earnings (P/E) multiple is north of 160, but when factoring its long-term growth (based on analyst expectations), its price-to-earnings-growth multiple is right around 1.0, indicating an excellent value for long-term investors.

2. Chipotle Mexican Grill

Shares of Chipotle Mexican Grill have been going in the wrong direction this year, as they're down more than 30%, but that doesn't mean that trend will continue.

This popular restaurant chain, which has been a growth beast in recent years, has been facing challenges in delivering impressive numbers of late. Although revenue rose by 3% in its most recent quarter (which ended June 30), Chipotle's same-store sales were down by 4%.

The company is confident it can rebound, as the upcoming quarter will reflect marketing initiatives it rolled out during the summer to help grow its business. In the longer term, it's eyeing growth opportunities in international markets, including Asia.

The stock's struggling performance this year gives you the chance to buy it at a much more reasonable valuation than in the past. Currently, Chipotle's stock trades at 28 times its estimated future profits (based on analyst expectations).

3. Marvell Technology

Marvell's stock trades at around $90, although it too has struggled this year, declining by 20% thus far. The custom chipmaker experienced volatility in its earnings, which has weighed on its performance.

For artificial intelligence (AI) investors, the name of the game is guidance, and when Marvell projected revenue that was less than what analysts expected for the current quarter, that led to a steep sell-off in late August.

However, the company has plenty of growth potential in AI, as its application-specific integrated circuits (ASICs) are customized chips that can serve as potential alternatives to higher-priced options from leading chipmaker Nvidia. During the six-month period ended Aug. 2, Marvell reported $3.9 billion in net revenue, an increase of 60% from the same period last year.

The stock trades at a forward P/E of less than 26, and it can be one of the better AI investments to load up on right now.