Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Cambiar SMID Fund Investor (CAMMX Quick QuoteCAMMX - Free Report) has a 0.92% expense ratio and 0.8% management fee. CAMMX is a Mid Cap Value mutual funds that aims to target medium-sized companies that possess strong value and income opportunities for investors. With yearly returns of 10.28% over the last five years, this fund clearly wins.

Parnassus Core Equity Investor (PRBLX Quick QuotePRBLX - Free Report) is a stand out amongst its peers. PRBLX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. With five-year annualized performance of 12.76%, expense ratio of 0.82% and management fee of 0.57%, this diversified fund is an attractive buy with a strong history of performance.

Transamerica Large Core I3 (TLATX Quick QuoteTLATX - Free Report) : 0.54% expense ratio and 0.45% management fee. TLATX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 11.31% over the last five years.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.