If you are on the hunt for big returns for your investment portfolio, then keep reading.

That's because listed below are two ASX 200 shares that have been named as buys and tipped to rise over 30% from current levels.

Here's why brokers are bullish on these big names:

Mineral Resources Ltd (ASX: MIN)

Bell Potter thinks that this mining and mining services company's shares are dirt cheap despite a strong rebound this week.

In response to Mineral Resources' quarterly update, the broker has reaffirmed its buy rating on the ASX 200 share with an improved price target of $29.50. Based on its current share price of $20.50, this implies potential upside of 44% for investors over the next 12 months.

Commenting on its buy recommendation, the broker said:

We maintain our Buy recommendation on valuation grounds. We continue to hold the view that (1) Onslow will be commissioned successfully, (2) associated Iron Ore & Services volumes will enable deleveraging of the balance sheet, (3) MIN has other options to manage its debt, including re-financing, and further asset sell downs, and (4) MIN's deleveraging will co-inside with it addressing its leadership and governance issues. Our Target Price is most sensitive to iron ore price. Long-term we apply US$95/t (62% CIF) vs the current spot of ~US$99/t. We share the view that iron ore will continue to see support in the US$80/t – US$100/t range.

ResMed Inc. (ASX: RMD)

Analysts at Goldman Sachs continue to believe that this sleep disorder treatment company's shares are being undervalued by the market.

The broker was pleased with ResMed's performance during the third quarter and particularly its gross margin improvement.

In response, Goldman reiterated its conviction buy rating on the ASX 200 share with an improved price target of $49.30. Based on its current share price of $36.77, this suggests that upside of 34% is possible for investors over the next 12 months.

Its analysts are bullish due to ResMed's strong growth outlook and the "unjustified" low multiples its shares trade on. It said:

RMD is the world's leading CPAP manufacturer of devices and masks in the treatment of OSA. The company has expanded to providing software services to out of hospital healthcare providers including Durable Equipment Manufacturers (DMEs), nursing homes and home health and hospice agencies. Our Buy recommendation on RMD is premised on (1) Ongoing robust new patient growth for CPAP therapy despite the market entry of GLP-1 drugs to treat OSA, (2) Further RMD market share gains, building on its #1 global market position, (3) Expansion of the OSA market in regions outside of the US. We believe the stock's current trading multiple is unjustified based on its growth outlook.