Looking to diversify your portfolio with some exposure to the mining sector?

If you are, then it could be worth checking out the two ASX 200 mining stocks listed below that are rated as buys by analysts at Goldman Sachs.

Here's what they are saying about them:

BHP Group Ltd (ASX: BHP)

The first ASX 200 mining stock that is being tipped as a buy is Australia's largest miner, BHP.

Goldman Sachs is very positive on the Big Australian and sees a lot of value in its shares at current levels. The broker has a buy rating and $47.40 price target on them, which implies potential upside of 21% for investors over the next 12 months.

It believes that BHP's shares are undervalued based on historical numbers. It said:

BHP is currently trading at ~0.8x NAV and ~6x NTM EBITDA, below the 25-yr average EV/EBITDA of 6.5-7x, but at a premium to RIO on ~5x and ~0.7x NAV. Over the last 10 years, BHP has traded at a ~0.5x premium to global mining peers. We believe this premium can be partly maintained due to ongoing superior margins and operating performance (particularly in Pilbara iron ore where BHP maintains superior FCF/t vs. peers).

Its analysts also highlight the company's growing exposure to copper as a reason to buy. They add:

We remain bullish on copper due to ongoing supply side challenges and increasing demand and expect BHP's copper EBITDA to increase by ~US$5bn to ~US$12bn by FY26E (~45% of group EBITDA). Under our base case, copper EBITDA is expected to reach US$20bn by FY35E, at GSe long run copper of US$4.57/lb (real $, from 2028).

Rio Tinto Ltd (ASX: RIO)

Goldman Sachs is also feeling bullish about mining giant Rio Tinto and sees it as an ASX 200 mining stock to buy.

The broker currently has a buy rating and $143.70 price target on its shares. This implies potential upside of almost 24% for investors from current levels.

Its analysts are positive on Rio Tinto due to its exposure to aluminium and copper. They said:

Attractive FCF and dividend yield + GS bullish copper and aluminium (EBITDA increasing to 45-50% by 2026): FCF/dividend yield of ~6% in 2025E and ~8%/~6% in 2026E driven by our bullish view on aluminium and copper (~45-50% of group EBITDA by 2026).

The broker also highlights the company's positive production growth outlook as a reason to buy. It adds:

RIO is a FCF and production growth story in our view, with forecast Cu Eq production growth of ~4-5% in 2025 & 2026 driven mostly by the ramp-up of the Oyu Tolgoi UG copper mine & a recovery at Escondida, higher Pilbara Fe shipments with the ramp-up of new mines, and a rebound in aluminium production.